Salt-tolerant star macromolecules

ABSTRACT

The present invention relates to multi-arm salt-tolerant star macromolecules, and methods of preparing and using the same. In one aspect of the invention, a salt-tolerant star macromolecule is capable of providing salt-tolerance to an aqueous composition.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Phase application of InternationalApplication No. PCT/US2014/014416, filed Feb. 3, 2014, which designatesthe United States and was published in English, which further claims thebenefit of priority to U.S. Provisional Application No. 61/760,210,filed Feb. 4, 2013. The foregoing related applications, in theirentirety, are incorporated herein by reference. This application furtherincorporates by reference, in their entirety, each of the following:U.S. Pat. No. 8,173,750, U.S. application Ser. No. 12/926,780, filedDec. 8, 2010, and U.S. Provisional Application No. 61/695,103, filedAug. 30, 2012.

FIELD OF THE INVENTION

The present invention relates salt-tolerant star macromolecules,salt-tolerant star macromolecule compositions and methods of making andusing the same.

SUMMARY OF THE INVENTION

The salt-tolerant star macromolecules of the present invention includemacromolecules comprising at least two different arms with at least onearm comprising a salt-tolerant-enhancing polymeric segment andcompositions comprising mixtures of salt-tolerant star macromoleculesand processes/methods of making and using the same. In addition, thepresent invention includes formulations and systems that incorporatesalt-tolerant star macromolecules and/or salt-tolerant starmacromolecule compositions as well as processes/methods of making andusing the same.

The salt-tolerant star macromolecules of the present invention includemacromolecules having a Salt Tolerance of at least 10,000 cP, at 0.3 wt% gel in a 0.4 wt % NaCl concentration.

The salt-tolerant star macromolecules of the present invention may besuitable for providing salt tolerancy, use as thickening agents, use asrheology modifiers, use in fracking fluids, use in mining applications,use in cosmetic and personal care applications, use in home careapplications, use in adhesive applications, use in electronicapplications, use in medical and pharmaceutical applications, use inpaper applications, or use in agricultural applications.

In one aspect the invention provides a polymer composition comprisingsalt-tolerant star macromolecules, each salt-tolerant star macromoleculehaving a core and five or more arms, wherein the number of arms within asalt-tolerant star macromolecule varies across the composition of starmolecules; and the arms on a star are covalently attached to the core ofthe star; each arm comprises one or more (co)polymer segments; and atleast one arm and/or at least one segment exhibits a differentsolubility from at least one other arm or one other segment,respectively, in a reference liquid of interest.

In one aspect of the invention, the salt-tolerant star macromolecule,emulsifier, gel, emulsifier-free emulsion, emulsion and/or thickeningagent, including those formed by a one-pot process, ATRP, CRP, and/orcombinations of one or more of these processes, may be used to provide acertain level of control over viscosity and consistency factors in manyaqueous and oil based systems including, for example, fracking fluidadditives, gelling agents, gels, proppant stabilizers, breakers,friction reducers, thickening agents.

In another aspect of the invention, the salt-tolerant starmacromolecules may be suitable in oil and gas applications, includingbut not limited to, as rheology modifiers for fracturing fluids/drillingwell fluids, gelling agents, gels, dispersants, proppant stabilizers andcarriers, breakers, friction reducers, lubricants, scale-buildupinhibitors, heat transfer fluids, thickening agents, additives toimprove oil extraction from oil sands, emulsion breakers foroil-sand-water emulsions, or additives to improve dewatering of oilsands.

In another aspect of the invention, the salt-tolerant starmacromolecules may be suitable in mining applications, including but notlimited to, dust suppressants, flocculating agents, gold and preciousmetal extraction, and precious metal processing, lubricants and dragreduction agents for pipeline slurry transport.

In another aspect of the invention, the salt-tolerant starmacromolecules may be suitable in cosmetic and personal careapplications, including but not limited to, cosmetic creams, lotions,gels, sprayable lotion, sprayable cream, sprayable gel, hair stylingsprays and mousses, hair conditioners, shampoos, bath preparations,ointments, deodorants, mascara, blush, lip stick, perfumes, powders,serums, skin cleansers, skin conditioners, skin emollients, skinmoisturizers, skin wipes, sunscreens, shaving preparations, solids, andfabric softeners.

In another aspect of the invention, the salt-tolerant starmacromolecules may be suitable in home care applications, including butnot limited to, cleaners for windows and glass, and other householdsurfaces, toilet areas, enzyme production, drain cleaners, liquid andgelled soaps, polishes and waxes, liquid and powdered detergentsincluding detergents for laundry and in dish washing.

In another aspect of the invention, the salt-tolerant starmacromolecules may be suitable in adhesive applications, including butnot limited to, associative complexes, billboard adhesives, carpetbacksizing compounds, hot melt adhesives, labeling adhesives, latexadhesives, leather processing adhesives, plywood laminating adhesives,paper adhesives, wallpaper pastes, wood glue.

In another aspect of the invention, the salt-tolerant starmacromolecules may be suitable in electronic applications, including butnot limited to, antistatic film and packaging, conductive inks, rheologycontrol agents used for copper foil production, multilayer ceramic chipcapacitors, photoresists, plasma display screens, lubricants for wire,cable, and optical fibers, gel lacquers for coil coating.

In another aspect of the invention, the salt-tolerant starmacromolecules may be suitable in medical and pharmaceuticalapplications, including but not limited to, but not limited to, medicaldevice lubrication, antibacterial coatings, pharmaceutical excipientssuch as binders, diluents, fillers, lubricants, glidants, disintegrants,polish agents, suspending agents, dispersing agents, plasticizers.

In another aspect of the invention, the salt-tolerant starmacromolecules may be suitable in paper applications, including but notlimited to, coatings, dispersion for tissue and thin papers, fillerretention and drainage enhancement, flocculation and pitch control,grease-proof coatings, adhesives, release coatings, surface sizing,sizes for gloss and ink holdout, tail tie and pickup adhesives forpapermaking.

In another aspect of the invention, the salt-tolerant starmacromolecules may be suitable in agricultural applications, includingbut not limited to, animal feed, dispersing agents, drift control,encapsulation, seed coatings, seed tape, spray adherents, water-basedsprays and spray emulsions, water-soluble packaging.

In another aspect of the invention, the salt-tolerant starmacromolecules may be suitable in other applications including but notlimited to, water- and solvent-based coating compositions, water- andsolvent-based lubricants, water- and solvent-based viscosity indexmodifiers, paints, plasticizers, antifoaming agents, antifreezesubstances, corrosion inhibitors, detergents, dental impressionmaterials, dental fillers, inkjet printer ink and other inks, ceramicand brick forming, prepolymers such as polyols for use in polyesters,polyurethanes, polycarbonates. For rheology modifier applications,characteristics are high gel strength, stability in the presence of saltand increased temperatures, high shear thinning characteristics, formsversatile low viscosity soluble concentrations, and synergisticinteractions with added agents to adjust their rheology profile tooptimize properties such as sedimentation, flow and leveling, sagging,spattering, etc.

In another aspect of the invention, there is a salt-tolerant starmacromolecule, or a method of making or using the same, that whendissolved in water at a concentration of at least 0.3 wt. % forms ahomogeneous gel and has a dynamic viscosity of at least 10,000 cP in a0.4 wt. % NaCl aqueous solution, such as a dynamic viscosity of at least25,000 cP in 0.2 wt. % NaCl aqueous solution, according to the SaltTolerance Test.

In another aspect of the invention, there is a salt-tolerant starmacromolecule, or a method of making or using the same, that whendissolved in water at a concentration of at least 0.3 wt. % forms ahomogeneous gel and has a dynamic viscosity in a NaCl-containing aqueoussolution that is greater than the dynamic viscosity at 0.0 wt. % NaClaqueous solution, such as having a maximum dynamic viscosity in anaqueous NaCl solution having a NaCl concentration other than 0.0 wt. %,or has an increase in dynamic viscosity with an increase in NaClconcentration, according to the Salt Tolerance Test.

In another aspect of the invention, there is a salt-tolerant starmacromolecule, or a method of making or using the same, that whendissolved in water at a concentration of at least 0.3 wt. % forms ahomogeneous gel and has a dynamic viscosity of at least 10,000 cP in a0.4 wt. % NaCl aqueous solution, according to the Salt Tolerance Test,and has a dynamic viscosity at 80° C. that is at least 50% relative toviscosity of the gel at 25° C., according to the Temperature StabilityTest, such as a dynamic viscosity at 60° C. that is at least 60%relative to viscosity of the gel at 25° C., according to the TemperatureStability Test.

In another aspect of the invention, there is a salt-tolerant starmacromolecule, or a method of making or using the same, that whendissolved in water at a concentration of at least 0.3 wt. % forms ahomogeneous gel and has a dynamic viscosity of at least 10,000 cP in a0.4 wt. % NaCl aqueous solution, according to the Salt Tolerance Test,wherein the salt-tolerant star macromolecule comprises:

-   -   i) a core;    -   ii) a plurality of hydrophilic polymeric arms; and    -   iii) at least one salt-tolerant-enhancing copolymeric arm,        comprising:        -   a) a hydrophilic polymeric polymerized segment proximal to            the core; and        -   b) a salt-tolerant-enhancing polymeric segment distal to the            core, wherein the salt-tolerant-enhancing polymeric segment            comprises: i) repeat units of monomeric residues of one or            more polymerized salt-tolerant-enhancing monomers; and ii)            optionally, repeat units of monomeric residues of one or            more polymerized hydrophobic or hydrophilic monomers.

In another aspect of the invention, there is a salt-tolerant starmacromolecule, or a method of making or using the same, that whendissolved in water at a concentration of at least 0.3 wt. % forms ahomogeneous gel and has a dynamic viscosity of at least 10,000 cP in a0.4 wt. % NaCl aqueous solution, according to the Salt Tolerance Test,wherein the salt-tolerant star macromolecule comprises:

-   -   i) a core;    -   ii) a plurality of hydrophilic polymeric arms; and    -   iii) at least one salt-tolerant-enhancing copolymeric arm,        comprising:        -   a) a hydrophilic polymeric polymerized segment proximal to            the core; and        -   b) a salt-tolerant-enhancing polymeric segment distal to the            core, wherein the salt-tolerant-enhancing polymeric segment            comprises: i) repeat units of monomeric residues of one or            more polymerized salt-tolerant-enhancing monomers; and ii)            optionally, repeat units of monomeric residues of one or            more polymerized hydrophobic or hydrophilic monomers;            wherein the salt-tolerant-enhancing polymeric segment            comprises in the range of between 5-35% of the monomeric            residues of one or more polymerized salt-tolerant-enhancing            monomers.

In another aspect of the invention, there is a salt-tolerant starmacromolecule, or a method of making or using the same, that whendissolved in water at a concentration of at least 0.3 wt. % forms ahomogeneous gel and has a dynamic viscosity of at least 10,000 cP in a0.4 wt. % NaCl aqueous solution, according to the Salt Tolerance Test,wherein the salt-tolerant star macromolecule comprises:

-   -   i) a core;    -   ii) a plurality of hydrophilic polymeric arms; and    -   iii) at least one salt-tolerant-enhancing copolymeric arm,        comprising:        -   a) a hydrophilic polymeric polymerized segment proximal to            the core; and        -   b) a salt-tolerant-enhancing polymeric segment distal to the            core, wherein the salt-tolerant-enhancing polymeric segment            comprises: i) repeat units of monomeric residues of one or            more polymerized salt-tolerant-enhancing monomers; and ii)            optionally, repeat units of monomeric residues of one or            more polymerized hydrophobic or hydrophilic monomers;            wherein the salt-tolerant-enhancing monomers comprise            ionizable monomers, anionic monomers, cationic monomers, or            hydrogen-bonding capable monomers.

In another aspect the invention, there is a salt-tolerant starmacromolecule, or a method of making or using the same, that whendissolved in water at a concentration of at least 0.3 wt. % forms ahomogeneous gel and has a dynamic viscosity of at least 10,000 cP in a0.4 wt. % NaCl aqueous solution, according to the Salt Tolerance Test,wherein the salt-tolerant star macromolecule is represented by FormulaZ:

wherein:

-   -   Core represents a crosslinked polymeric segment;    -   P1 represents a hydrophilic polymeric segment comprised of        repeat units of monomeric residues of one or more polymerized        hydrophilic monomers;    -   P2 independently represents a salt-tolerant-enhancing polymeric        segment comprising repeat units of:        -   a) monomeric residues of one or more polymerized            salt-tolerant-enhancing monomers; and        -   b) optionally, monomeric residues of one or more polymerized            hydrophobic or hydrophilic monomers;    -   P3 independently represents a hydrophilic polymeric segment        comprised of repeat units of monomeric residues of one or more        polymerized hydrophilic monomers;    -   P4 represents a hydrophobic polymeric segment comprised of        repeat units of monomeric residues of one or more polymerized        hydrophobic monomers;    -   P5 represents a hydrophilic polymeric segment comprised of        repeat units of monomeric residues of one or more polymerized        hydrophilic monomers;    -   q1 represents the number of repeat units in P1 and has a value        between 10 and 2000;    -   q2 independently represents the number of repeat units in P2 and        has a value between 10 and 500;    -   q3 independently represents the number of repeat units in P3 and        has a value between 10 and 2000;    -   q4 represents the number of repeat units in P4 and has a value        between 10 and 500;    -   q5 represents the number of repeat units in P5 and has a value        between 10 and 2000;    -   r represents the number of polymeric arms covalently attached to        the Core and has a value in the range of from 0 to 1000;    -   s independently represents the number of salt-tolerant-enhancing        copolymeric arms covalently attached to the Core and has a value        in the range of from 1 to 1000;    -   t represents the number of copolymeric arms covalently attached        to the Core and has a value in the range of from 0 to 1000; and    -   n represents the number of salt-tolerant-enhancing arm types        covalently attached to the Core and has a value of at least 1;        wherein:    -   i) the molar ratio of:        -   a) r to s is in the range of between 40:1 and 1:40;        -   b) the molar ratio of r to t is in the range of between 40:1            and 1:40;        -   c) the molar ratio of t to s is in the range of between 40:1            and 1:40;        -   d) the molar ratio of r to (s+t) is in the range of between            40:1 and 1:40; or        -   e) combinations thereof; and    -   ii) r and t cannot both equal zero unless n represents a value        of at least 2.

In another aspect the invention, there is a salt-tolerant starmacromolecule, or a method of making or using the same, that whendissolved in water at a concentration of at least 0.3 wt. % forms ahomogeneous gel and has a dynamic viscosity of at least 10,000 cP in a0.4 wt. % NaCl aqueous solution, according to the Salt Tolerance Test,wherein the salt-tolerant star macromolecule is a mikto starmacromolecule.

In another aspect the invention, there is a salt-tolerant starmacromolecule, or a method of making or using the same, that whendissolved in water at a concentration of at least 0.3 wt. % forms ahomogeneous gel and has a dynamic viscosity of at least 10,000 cP in a0.4 wt. % NaCl aqueous solution, according to the Salt Tolerance Test,wherein the salt-tolerant star macromolecule has a molecular weight (Mn)in the range of from 5,000 g/mol to 10,000,000 g/mol, or the arms of thesalt-tolerant star macromolecule independently have a molecular weight(Mn) in the range of from 1,000 g/mol to 250,000 g/mol.

In another aspect the invention, there is a salt-tolerant starmacromolecule, or a method of making or using the same, that whendissolved in water at a concentration of at least 0.3 wt. % forms ahomogeneous gel and has a dynamic viscosity of at least 10,000 cP in a0.4 wt. % NaCl aqueous solution, according to the Salt Tolerance Test,wherein the salt-tolerant star macromolecule has a viscosity of greaterthan 40,000 cP at a pH between 6 to 11, or has a viscosity of less than5,000 cP at a shear rate of 4 sec⁻¹.

In another aspect the invention, there is a salt-tolerant starmacromolecule comprising a mixture of 2 or more arm types, such as 3 ormore arm types, that when dissolved in water at a concentration of atleast 0.3 wt. % forms a homogeneous gel and has a dynamic viscosity ofat least 10,000 cP in a 0.4 wt. % NaCl aqueous solution, according tothe Salt Tolerance Test. For example, the 2 or more arm types, such as 3or more arm types, of the salt-tolerant star macromolecule may comprisehomopolymeric arm types, copolymeric arm types, hydrophilic arm types,hydrophobic arm types, salt-tolerant-enhancing arm types, orcombinations, mixtures, or varying molar ratios thereof. The 2 or morearm types, such as 3 or more arm types, of the salt-tolerant starmacromolecule may comprise varying degrees of polymerization. In anotheraspect the invention, the dynamic viscosity of the salt-tolerant starmacromolecule comprising a mixture of 2 or more arm types, such as 3 ormore arm types, may be dependent on the molar ratio of the mixture ofarm types of said salt-tolerant star macromolecule, according to theSalt Tolerance Test, or may be NaCl concentration dependent, accordingto the Salt Tolerance Test, or combinations thereof.

In another aspect the invention, there is a salt-tolerant thickeningagent, or a method of making or using the same, comprising asalt-tolerant star macromolecule that when dissolved in water at aconcentration of at least 0.3 wt. % forms a homogeneous gel and has adynamic viscosity of at least 10,000 cP in a 0.4 wt. % NaCl aqueoussolution, such as a dynamic viscosity of at least 25,000 cP in 0.2 wt. %NaCl aqueous solution, according to the Salt Tolerance Test.

In another aspect the invention, there is a method of making asalt-tolerant composition, comprising: adding the salt-tolerant starmacromolecule that when dissolved in water at a concentration of atleast 0.3 wt. % forms a homogeneous gel and has a dynamic viscosity ofat least 10,000 cP in a 0.4 wt. % NaCl aqueous solution, such as adynamic viscosity of at least 25,000 cP in 0.2 wt. % NaCl aqueoussolution, according to the Salt Tolerance Test.

In another aspect the invention, there is a method of making an aqueouscomposition salt-tolerant, comprising: adding the salt-tolerant starmacromolecule that when dissolved in water at a concentration of atleast 0.3 wt. % forms a homogeneous gel and has a dynamic viscosity ofat least 10,000 cP in a 0.4 wt. % NaCl aqueous solution, such as adynamic viscosity of at least 25,000 cP in 0.2 wt. % NaCl aqueoussolution, according to the Salt Tolerance Test.

In another aspect the invention, there is a one-pot method of preparinga star macromolecule, comprising:

-   -   i) preparing one or more of a first arm, comprising:        -   a) feeding a first amount of a radical initiator in a            controlled manner to a reaction vessel containing a first            group of monomers at a pre-determined temperature; and        -   b) polymerizing the first group of monomers to greater than            15% monomer conversion;    -   ii) preparing one or more of a second arm and, optionally,        extending the prepared one or more first arms, comprising:        -   a) adding a second arm initiator to the reaction vessel;        -   b) adding a second group of monomers to the reaction vessel;        -   c) feeding a second amount of the radical initiator in a            controlled manner to the reaction vessel containing the            second arm initiator, the second group of monomers, and            optionally the prepared one or more first arms, at a            pre-determined temperature; and        -   d) polymerizing the second group of monomers to greater than            70% monomer conversion;    -   iii) optionally, repeating step ii) to prepare one or more of a        third arm;    -   iv) crosslinking the prepared one or more first arms, the        prepared one or more second arms, and optionally, the prepared        one or more third arms; and    -   v) isolating the prepared star macromolecule.

In another aspect the invention, there is a one-pot method of preparinga star macromolecule, comprising:

-   -   i) preparing one or more of a first arm, comprising:        -   a) feeding a first amount of a radical initiator in a            controlled manner to a reaction vessel containing a first            group of monomers at a pre-determined temperature; and        -   b) polymerizing the first group of monomers to greater than            15% monomer conversion;    -   ii) preparing one or more of a second arm and, optionally,        extending the prepared one or more first arms, comprising:        -   a) adding a second arm initiator to the reaction vessel;        -   b) adding a second group of monomers to the reaction vessel;        -   c) feeding a second amount of the radical initiator in a            controlled manner to the reaction vessel containing the            second arm initiator, the second group of monomers, and            optionally the prepared one or more first arms, at a            pre-determined temperature; and        -   d) polymerizing the first group of monomers to greater than            70% monomer conversion;    -   iii) optionally, repeating step ii) to prepare one or more of a        third arm;    -   iv) crosslinking the prepared one or more first arms, the        prepared one or more second arms, and optionally, the prepared        one or more third arms; and    -   v) isolating the prepared star macromolecule;        wherein the one-pot method reduces the preparation time by at        least 75%, relative to multi-pot preparations, is exclusive of        intermediate purification steps, or consists of one washing step        after crosslinking.

In one aspect of the invention, there is a salt-tolerant starmacromolecule, or a method of making or using the same, comprising: aplurality of arms comprising at least two types of arms, wherein afirst-arm-type extends beyond a second-arm-type and said first-arm-typehas a salt-tolerant-enhancing segment on its distal end, wherein atleast a portion of the salt-tolerant-enhancing segment may extend beyondthe length of the second-arm-types either by the size of the monomericsegment or segments (which may be varied by length of monomeric residue,degree of polymerization, and/or both) for which thesalt-tolerant-enhancing segment is attached.

In one aspect of the invention, there is a salt-tolerant starmacromolecule, or a method of making or using the same, comprising: aplurality of arms comprising at least three types of arms, wherein afirst-arm-type extends beyond a second-arm-type and said first-arm-typehas a salt-tolerant-enhancing segment (homopolymeric or copolymeric) onits distal end, wherein at least a portion of thesalt-tolerant-enhancing segment may extend beyond the length of thesecond-arm-types either by the size of the monomeric segment or segments(which may be varied by length of monomeric residue, degree ofpolymerization, and/or both) for which the salt-tolerant-enhancingsegment is attached; and wherein a third-arm-type extends beyond asecond-arm-type and said third-arm-type has a hydrophobic segment(homopolymeric or copolymeric) on its distal end, wherein at least aportion of the hydrophobic segment (homopolymeric or copolymeric) mayextend beyond the length of the second-arm-types either by the size ofthe monomeric segment or segments (which may be varied by length ofmonomeric residue, degree of polymerization, and/or both) for which thehydrophobic segment (homopolymeric or copolymeric) is attached.

Recognizing that the “length” of an arm or segment and the “extendingbeyond” limitation may be theoretical, meaning that while it is notempirically measured it is understood to “extend beyond” and/or have alonger “length” relative to the length of the second-arm-type if thedegree of polymerization is greater for monomeric residues of the sametype or of the same theoretical length.

In one aspect of the invention, there is a salt-tolerant starmacromolecule, or a method of making or using the same, comprising: aplurality of arms comprising at least two types of arms, wherein thedegree of polymerization of a first-arm-type is greater than the degreeof polymerization of a second-arm-type, and wherein said first-arm-typehas a distal end portion that is salt-tolerant-enhancing. In anotheraspect of the invention, this star macromolecule may be formed by firstforming or obtaining the salt-tolerant-enhancing portion then formingthe remaining portion of the first-arm-type from the end of thesalt-tolerant-enhancing portion and the second-arm-type, in a one-potsynthesis, wherein the polymerization of the second portion of thefirst-arm-type is commenced prior to the initialization of thesecond-arm-type but there is at least some point wherein portions, e.g.,substantial portions, of the first-arm-type and second-arm-type arebeing polymerically extended simultaneously.

In one aspect of the invention, there is a salt-tolerant starmacromolecule, or a method of making or using the same, comprising: aplurality of arms comprising at least three types of arms, wherein thedegree of polymerization of a first-arm-type and a third-arm-type aregreater than the degree of polymerization of a second-arm-type, andwherein said first-arm-type and said third-arm-type have a distal endportion that is hydrophobic and salt-tolerant-enhancing, respectively.In another aspect of the invention, this star macromolecule may beformed by first forming or obtaining the hydrophobic portion and thesalt-tolerant-enhancing portion then forming the remaining portion ofthe first-arm-type from the end of the hydrophobic, the third-arm-typefrom the end of the salt-tolerant-enhancing portion, and thesecond-arm-type, in a one-pot synthesis, wherein the polymerization ofthe second portion of the first-arm-type and the second portion of thethird-arm-type are commenced prior to the initialization of thesecond-arm-type but there is at least some point wherein portions, e.g.,substantial portions, of the first-arm-type, third-arm-type, andsecond-arm-type are being polymerically extended simultaneously.

In one aspect of the invention, there is an oil-soluble, salt-tolerantstar macromolecule, or a method of making or using the same, comprising:a plurality of different arms comprising at least two types of arms,wherein a first-arm-type extends beyond a second-arm-type and saidfirst-arm-type has a salt-tolerant-enhancing segment (homopolymeric orcopolymeric) on its distal end, and said second-arm-type has ahydrophilic segment on its distal end.

In one aspect of the invention, there is an oil-soluble, salt-tolerantstar macromolecule, or a method of making or using the same, comprising:a plurality of different arms comprising at least three types of arms,wherein a first-arm-type extends beyond a second-arm-type and saidfirst-arm-type has a salt-tolerant-enhancing segment (homopolymeric orcopolymeric) on its distal end, and the second-arm-type has ahydrophilic segment on its distal end, and wherein a third-arm-typeextends beyond said second-arm-type and the third-arm-type has ahydrophobic segment (homopolymeric or copolymeric) on its distal end.

In one aspect of the invention, there is an oil-soluble, salt-tolerantstar macromolecule, or a method of making or using the same, comprising:a plurality of arms comprising at least two types of arms, wherein thedegree of polymerization of a first-arm-type is greater than the degreeof polymerization of a second-arm-type, and wherein said first-arm-typehas a salt-tolerant-enhancing segment on its distal end, and whereinsaid second-arm-type has a hydrophilic segment on its distal end.

In one aspect of the invention, there is an oil-soluble, salt-tolerantstar macromolecule, or a method of making or using the same, comprising:a plurality of arms comprising at least three types of arms, wherein thedegree of polymerization of a first-arm-type is greater than the degreeof polymerization of a second-arm-type, and wherein said first-arm-typehas a salt-tolerant-enhancing segment on its distal end, and whereinsaid second-arm-type has a hydrophilic segment on its distal end, andwherein the degree of polymerization of a third-arm-type is greater thanthe degree of polymerization of the second-arm-type, and wherein saidthird-arm-type has a hydrophobic (homopolymeric or copolymeric) on itsdistal end.

In one aspect of the invention, there is a salt-tolerant starmacromolecule, or a method of making or using the same, comprising: aplurality of arms comprising at least two types of arms, wherein thedegree of polymerization of a first-arm-type is greater than the degreeof polymerization of a second-arm-type, and wherein said first-arm-typehas a distal end portion that is salt-tolerant-enhancing, and theproximal portion of the first-arm-type and the second-arm-type are thesame with the only difference between the first-arm-type and thesecond-arm-type being that the first-arm-type has asalt-tolerant-enhancing portion on its distal end. In another aspect ofthe invention, this star macromolecule may be formed by first forming orobtaining the salt-tolerant-enhancing portion and then forming theremaining portion of the first-arm-type from the end of thesalt-tolerant-enhancing portion, and the second-arm-type simultaneouslyin a one-pot synthesis.

In one aspect of the invention, there is a salt-tolerant starmacromolecule, or a method of making or using the same, comprising: aplurality of arms comprising at least three types of arms, wherein thedegree of polymerization of a first-arm-type and third-arm-type aregreater than the degree of polymerization of a second-arm-type, andwherein said first-arm-type and third-arm-type have a distal end portionthat is salt-tolerant-enhancing and hydrophobic, respectively, and theproximal portion of the first-arm-type and the third-arm-type and thesecond-arm-type are the same with the only difference between thefirst-arm-type and the third-arm-type and the second-arm-type being thatthe first-arm-type and the third-arm-type have a salt-tolerant-enhancingand hydrophobic portion on their distal ends, respectively. In anotheraspect of the invention, this star macromolecule may be formed by firstforming or obtaining the salt-tolerant-enhancing portion and thehydrophobic portion and then forming the remaining portion of thefirst-arm-type and third-arm-type from the end of thesalt-tolerant-enhancing and hydrophobic portion, respectively, and thesecond-arm-type simultaneously in a one-pot synthesis.

BRIEF DESCRIPTION OF THE FIGURES

The following figures exemplify aspects of the disclosed process but donot limit the scope of the process to the examples discussed.

FIG. 1. GPC curve for the poly(styrene-co-tert-butyl methacrylate)macroinitiator formed in step 1 of the synthesis of an exemplary(St₁₉-co-MAA₄)-b-AA₃₂₅/AA₉₈) star macromolecule.

FIG. 2. GPC curve of the St₁₉-co-tBMA₄) macroinitiator and the mixtureof formed block copolymer arms (St₁₉-co-tBMA₄)-b-tBA₃₂₅ and homopolymerarms tBA₉₈ in step 2 of the synthesis of an exemplary((St₁₉-co-MAA₄)-b-AA₃₂₅/AA₉₈) star macromolecule.

FIG. 3. GPC curves before and after the crosslinking of mixture of blockcopolymer arms and homopolymeric arms (St₁₉-co-tBMA₄)-b-tBA₃₂₅/tBA₉₈ instep 3 of the synthesis of an exemplary ((St₁₉-co-MAA₄)-b-AA₃₂₅/AA₉₈)star macromolecule.

FIG. 4. Comparison of viscosity vs. shear rate of aqueous solution ofseven different polymers: Carbopol, Advantomer (from Example 1),((St₁₉-co-MAA₄)-b-AA₃₂₅/AA₉₈) star (from Example 2),(MMA₁₅-b-AA₃₆₇/AA₈₂) star (from Example 3), (MMA₂₂-b-AA₇₆₂/AA₅₉) star(from Example 4), (MMA₁₅-b-AA₆₁₇/St₁₆-b-AA₆₁₇/AA₈₆) (7/3) star (fromExample 5) and (MMA₁₅-b-AA₆₇₆/St₁₆-b-AA₆₇₆/AA₅₈) (9/1) star (fromExample 6).

FIG. 5. Dependence of the viscosity on the salt concentration foraqueous solutions of six different polymers: Carbopol, Advantomer (fromExample 1), ((St₁₉-co-MAA₄)-b-AA₃₂₅/AA₉₈) star (from Example 2),(MMA₁₅-b-AA₃₆₇/AA₈₂) star (from Example 3), (MMA₂₂-b-AA₇₆₂/AA₅₉) star(from Example 4), and (MMA₁₅-b-AA₆₁₇/St₁₆-b-AA₆₁₇/AA₈₆) (7/3) star (fromExample 5).

FIG. 6. Dependence of the viscosity on the temperature for aqueoussolutions of six different polymers: Carbopol, Advantomer (from Example1), ((St₁₉-co-MAA₄)-b-AA₃₂₅/AA₉₈) star (from Example 2),(MMA₁₅-b-AA₃₆₇/AA₈₂) star (from Example 3), (MMA₂₂-b-AA₇₆₂/AA₅₉) star(from Example 4), and (MMA₁₅-b-AA₆₁₇/St₁₆-b-AA₆₁₇/AA₈₆) (7/3) star (fromExample 5).

FIG. 7. An images demonstrating phase separated water and sunflower oil(left) and the emulsifying properties of (MMA₂₂-b-AA₇₆₂/AA₅₉) star (fromExample 4) (right).

FIG. 8. Dependence of the viscosity on the salt concentration foraqueous solutions of four different polymers in river water: Carbopol,Advantomer (from Example 1), (MMA₁₅-b-AA₃₆₇/AA₈₂) star (from Example 3)and (MMA₁₅-b-AA₆₁₇/St₁₆-b-AA₆₁₇/AA₈₆) (7/3) star (from Example 5).

FIG. 9. Dependence of the viscosity on pH for aqueous solutions of twopolymers: Carbopol and (MMA₁₅-b-AA₆₇₆/St₁₆-b-AA₆₇₆/AA₅₈) (9/1) star(from Example 6).

DETAILED DESCRIPTION OF THE INVENTION

The term “solubility” or “soluble” is understood to mean that when acomponent is mixed into a solvent and tested, at STP in a 1 cm cuvette,it has a light transmittance value, at a wavelength at or around aUV/Vis minimum wavelength for the mixture, of at least 40%, for example,at least 50%, 70%, 85%, or at least 95%.

The term “clear” as is used to describe a homogenous gel or homogenoussolution is understood to mean that when the gel or solution is tested,at STP in a 1 cm cuvette, it has a light transmittance value, at awavelength at or around a UV/Vis minimum wavelength for the gel orsolution, of at least 40%, for example, at least 50%, 70%, 85%, or atleast 95%.

The term “water-soluble monomer” is understood to mean a monomer havingat least about 10 wt. % solubility in water at STP. For example, a watersoluble monomer may have at least 15 wt. %, 20 wt. %, 25 wt. %, or atleast 30 wt. % solubility in water at STP.

The term “water-insoluble monomer” is understood to mean a monomerhaving less water solubility than a water soluble monomer, for example,less that about 5 wt. %, such as less than 1 wt. % or 0.5 wt. %solubility in water at STP.

The term “water-soluble star macromolecule” is understood to mean a starmacromolecule that is soluble in water, pH adjusted if necessary to a pHof no greater than 8 with sodium hydroxide, at a concentration of atleast 5 g/L, for example, between 8 g/L to 100 g/L, such as, at least 10g/L, 12 g/L, 15 g/L, or at least 20 g/L. For example, a water-solublestar macromolecule having an aqueous solubility of at least 10 g/L mayinclude the introduction of at least 10 g of the star macromolecule intoapproximately 1 L of water, neutralizing the mixture, if necessary, byadjusting the pH of the resulting mixture to about pH 8 (e.g., with theaddition of base, such as sodium hydroxide), and vigorously stirring ata temperature no greater than 100° C. for no more than about 60 minutes,to achieve dissolution of the star macromolecule, and testing thesolubility at STP.

The term “oil-soluble star macromolecule” is understood to mean a starmacromolecule that is soluble in mineral oil at a concentration of atleast 5 g/L, for example, between 8 g/L to 100 g/L, such as, at least 10g/L, 12 g/L, 15 g/L, or at least 20 g/L of mineral oil. For example, anoil-soluble star macromolecule having an oil solubility of at least 10g/L may include the introduction of at least 10 g of the starmacromolecule into approximately 1 L of mineral oil, and vigorouslystirring at a temperature no greater than 100° C. for no more than about60 minutes, to achieve dissolution of the star macromolecule, andtesting the solubility at STP.

The term “hydrophilic” is understood to mean, in relation to a material,such as a polymeric arm, or a polymeric segment of a polymeric arm, thatthe material is water soluble and comprises hydrophilic segments havingan HLB equal to or greater than 8, for example, an HLB equal to 16-20,or equal to or greater than 18, 19, or 19.5. In certain embodiments, thehydrophilic segment may comprise at least 75 mol % of water-solublemonomer residues, for example, between 80 mol % to 100 mol % or at least85 mol %, 90 mol %, 95 mol %, or at least 97 mol % water-soluble monomerresidues.

The term “hydrophobic” is understood to mean, in relation to a material,such as a polymeric arm, or a polymeric segment of a polymeric arm, thatthe material is water insoluble and comprises hydrophilic segmentshaving an HLB less than 8, for example, an HLB less than 7. In certainembodiments, the hydrophobic segment may comprise at least 75 mol % ofwater-insoluble monomer residues, for example, between 80 mol % to 100mol % or at least 85 mol %, 90 mol %, 95 mol %, or at least 97 mol %water-insoluble monomer residues.

The term “monomer residue” or “monomeric residue” is understood to meanthe residue resulting from the polymerization of the correspondingmonomer. For example, a polymer derived from the polymerization of anacrylic acid monomer (or derivatives thereof, such as acid protectedderivatives of acrylic acid including but not limited to t-butyl esterof acrylic acid), will provide polymeric segments, identified as PAA,comprising repeat units of monomeric residues of acrylic acid, i.e.,“—CH(CO₂H)CH₂—”. For example, a polymer derived from the polymerizationof styrene monomers will provide polymeric segments, identified as PSt,comprising repeat units of monomeric residues of styrene, i.e.,“—CH(C₆H₅)CH₂—.” For example, a polymer derived from the polymerizationof monomeric divinylbenzene monomers will provide polymeric segmentscomprising repeat units of monomeric residues of divinylbenzene, i.e.,“—CH₂CH(C₆H₅)CHCH₂—.”

The term “emulsifier” is understood to mean a component that comprisesan appreciable weight percent of an amphiphilic compound having amolecular weight of less than 5,000 MW. Emulsifiers are usually linearorganic compounds that contain both hydrophobic portions (tails) andhydrophilic portions (heads), i.e., are amphiphilic. Examples ofemulsifiers include but are not limited to: alkyl benzenesulfonates,alkanesulfonates, olefin sulfonates, alkylethersulfonates, glycerolether sulfonates, α-methyl ester sulfonates, sulfofatty acids, alkylsulfates, fatty alcohol ether sulfates, glycerol ether sulfates, hydroxymixed ether sulfates, monoglyceride (ether) sulfates, fatty acid amide(ether) sulfates, mono- and dialkylsulfosuccinates, mono- anddialkylsulfosuccinamates, sulfotriglycerides, ether carboxylic acids andsalts thereof, fatty acid isethionates, fatty acid sarcosinates, fattyacid taurides, acyl lactylates, acyl tartrates, acyl glutamates, acylaspartates, alkyl oligoglucoside sulfates, protein fatty acidcondensates (particularly wheat-based vegetable products) and alkyl(ether) phosphates, alkylbetaines, alkylamidobetaines, aminopropionates,aminoglycinates, imidazoliniumbetaines and sulfobetaines.

The term “emulsifier-free” is understood to mean a composition ormixture wherein the formulation is substantially devoid of anyemulsifiers, for example less than 0.1 wt. % of emulsifier, relative tothe total composition, or less than 0.05 wt. % of emulsifier, relativeto the total composition, or less than 0.01 wt. % of emulsifier,relative to the total composition, or a formulation where there is noemulsifier.

The term “STP” is understood to mean standard conditions for temperatureand pressure for experimental measurements, wherein the standardtemperature is a temperature of 25° C. and the standard pressure is apressure of 1 atm.

The term “hydroxyl” and “hydroxy” is understood to mean the functionalgroup —OH.

The term “salt-tolerant-enhancing” is understood to mean any monomer,polymer, polymeric segment, or star macromolecules having an ionizablefunctional group, an anionic functional group, a cationic functionalgroup, or a hydrogen-bonding capable functional group, such as ahydrogen bond donating functional group or a hydrogen bond acceptingfunctional group.

In certain embodiments, the salt-tolerant star macromolecules of thepresent invention, when dissolved in water at a concentration of atleast 0.3 wt. % form a homogeneous gel and have a dynamic viscosity ofat least 10,000 cP in a 0.4 wt. % NaCl aqueous solution, according tothe Salt Tolerance Test, for example, have a dynamic viscosity of atleast 15,000 cP in a 0.4 wt. % NaCl aqueous solution, such as between10,000 cP and 150,000 cP; between 10,000 cP and 125,000 cP; between10,000 cP and 100,000 cP; between 10,000 cP and 75,000 cP; between10,000 cP and 50,000 cP; between 10,000 cP and 40,000 cP; between 30,000cP and 100,000 cP; or between 50,000 cP and 150,000 cP, in a 0.4 wt. %NaCl aqueous solution, according to the Salt Tolerance Test. Thesalt-tolerant star macromolecules of the present invention, whendissolved in water at a concentration of at least 0.3 wt. %, forexample, at least 0.35 wt. %, such as at least 0.4 wt. %, at least 0.45wt. %, or at least 0.5 wt. %, form a homogeneous gel and have a dynamicviscosity of at least 10,000 cP in a 0.4 wt. % NaCl aqueous solution,according to the Salt Tolerance Test. The salt-tolerant starmacromolecules of the present invention, when dissolved in water at aconcentration of at least 0.3 wt. % form a homogeneous gel and have adynamic viscosity of at least 10,000 cP in a 0.4 wt. % NaCl aqueoussolution, according to the Salt Tolerance Test, for example, have adynamic viscosity of at least 10,000 cP in a 0.45 wt. % NaCl aqueoussolution, such as in a 0.5 wt. %; 0.55 wt. %; 0.6 wt. %; 0.65 wt. %; 0.7wt. %; 0.75 wt. %; 0.8 wt. %; 0.85 wt. %; 0.9 wt. %; 0.95 wt. %; or 1.0wt. % NaCl aqueous solution, according to the Salt Tolerance Test.

In certain embodiments, the salt-tolerant star macromolecules of thepresent invention, when dissolved in water at a concentration of atleast 0.3 wt. % form a homogeneous gel and have a dynamic viscosity ofat least 25,000 cP in 0.2 wt. % NaCl aqueous solution, according to theSalt Tolerance Test, for example, have a dynamic viscosity of at least30,000 cP in a 0.5 wt. % NaCl aqueous solution, such as between 25,000cP and 150,000 cP; between 25,000 cP and 125,000 cP; between 25,000 cPand 100,000 cP; between 25,000 cP and 75,000 cP; between 25,000 cP and50,000 cP; between 25,000 cP and 40,000 cP; between 30,000 cP and100,000 cP; or between 50,000 cP and 150,000 cP, in a 0.2 wt. % NaClaqueous solution, according to the Salt Tolerance Test.

In certain embodiments, the salt-tolerant star macromolecules of thepresent invention, when dissolved in water at a concentration of atleast 0.3 wt. % form a homogeneous gel and have a dynamic viscosity in aNaCl-containing aqueous solution that is greater than the dynamicviscosity at 0.0 wt. % NaCl aqueous solution, according to the SaltTolerance Test, for example, have a maximum dynamic viscosity in anaqueous NaCl solution having a NaCl concentration other than 0.0 wt. %,according to the Salt Tolerance Test, such as a maximum dynamicviscosity in an aqueous NaCl solution having a NaCl concentration ofgreater than 0.05 wt. % NaCl, such as between 0.05 wt. % and 5 wt. %NaCl concentration; between 0.05 wt. % and 4 wt. %; between 0.05 wt. %and 3 wt. %; between 0.05 wt. % and 2 wt. %; between 0.05 wt. % and 1wt. %; between 0.05 wt. % and 0.5 wt. %; between 0.1 wt. % and 5 wt. %;between 0.2 wt. % and 2.5 wt. %; or between 0.15 wt. % and 1 wt. %. Incertain embodiments, the salt-tolerant star macromolecule has a dynamicviscosity in 0.01-0.5 wt. % NaCl aqueous solution greater than thedynamic viscosity in a 0.0 wt. % NaCl aqueous solution, according to theSalt Tolerance Test, such as a dynamic viscosity in 0.1 wt. % NaClaqueous solution greater than the dynamic viscosity in a 0.05 wt. % NaClaqueous solution, according to the Salt Tolerance Test. In certainembodiments, the salt-tolerant star macromolecule, when dissolved inwater at a concentration of at least 0.3 wt. % form a homogeneous gel,has an increase in dynamic viscosity with an increase in NaClconcentration, according to the Salt Tolerance Test, such as a dynamicviscosity that increases with increasing NaCl concentration, accordingto the Salt Tolerance Test.

In certain embodiments, the salt-tolerant star macromolecules of thepresent invention, when dissolved in water at a concentration of atleast 0.3 wt. % form a homogeneous gel and has a dynamic viscosity in a0.1 wt. % NaCl aqueous solution that is at least 50% of the dynamicviscosity at 0.0 wt. % NaCl aqueous solution, according to the SaltTolerance Test, for example, at least 60%, such as at least 65%; atleast 70%; at least 75%; at least 80%; at least 90%; at least 100%; orgreater than 100% of the dynamic viscosity at 0.0 wt. % NaCl aqueoussolution, according to the Salt Tolerance Test.

In certain embodiments, the salt-tolerant star macromolecules of thepresent invention, when dissolved in water at a concentration of atleast 0.3 wt. % form a homogeneous gel and has a dynamic viscosity in a0.2 wt. % NaCl aqueous solution that is at least 25% of the dynamicviscosity at 0.0 wt. % NaCl aqueous solution, according to the SaltTolerance Test, for example, at least 30%, such as at least 40%; atleast 50%; at least 60%; at least 75%; at least 90%; at least 100%; orgreater than 100% of the dynamic viscosity at 0.0 wt. % NaCl aqueoussolution, according to the Salt Tolerance Test. In certain embodiments,the salt-tolerant star macromolecule has a dynamic viscosity of thesalt-tolerant star macromolecule in a 0.4 wt. % NaCl aqueous solution isat least 30% of the dynamic viscosity at 0.0 wt. % NaCl aqueoussolution, according to the Salt Tolerance Test, for example, at least35%, such as at least 40%; at least 45%; at least 50%; at least 55%; atleast 60%; at least 75%; at least 80%; at least 90%; or greater than100% of the dynamic viscosity at 0.0 wt. % NaCl aqueous solution,according to the Salt Tolerance Test.

In certain embodiments, the salt-tolerant star macromolecules of thepresent invention, when dissolved in water at a concentration of atleast 0.3 wt. % form a homogeneous gel and have a dynamic viscosity ofat least 10,000 cP in a 0.5 wt. % NaCl aqueous solution, according tothe Salt Tolerance Test, and have a dynamic viscosity at 80° C. is atleast 50% relative to viscosity of the gel at 25° C., according to theTemperature Stability Test, for example at least 55%, such as at least60%; at least 70%; at least 80%; or at least 90%, relative to viscosityof the gel at 25° C., according to the Temperature Stability Test.

In certain embodiments, the salt-tolerant star macromolecules of thepresent invention, when dissolved in water at a concentration of atleast 0.3 wt. % form a homogeneous gel and have a dynamic viscosity ofat least 10,000 cP in a 0.5 wt. % NaCl aqueous solution, according tothe Salt Tolerance Test, and have a dynamic viscosity at 60° C. is atleast 60% relative to viscosity of the gel at 25° C., according to theTemperature Stability Test, for example at least 65%, such as at least70%; at least 75%; at least 80%; or at least 90%, relative to viscosityof the gel at 25° C., according to the Temperature Stability Test.

In certain embodiments, the salt-tolerant star macromolecules of thepresent invention, comprise: i) a core, such as a hydrophobic core or ahydrophilic core; ii) a plurality of hydrophilic polymeric arms; andiii) at least one salt-tolerant-enhancing copolymeric arm, comprising:a) a hydrophilic polymeric polymerized segment proximal to the core; andb) a salt-tolerant-enhancing polymeric segment distal to the core. Incertain embodiments, the one or more of the arms of the plurality ofhydrophilic polymeric arms of the salt-tolerant star macromolecule maycomprise a hydrophilic homopolymeric arm or a hydrophilic copolymericarm, for example, a block copolymeric arm, a gradient copolymeric arm,or a random copolymeric arm.

In certain embodiments, the salt-tolerant-enhancing polymeric segmentdistal to the core may comprise a salt-tolerant-enhancing homopolymericsegment or a salt-tolerant-enhancing copolymeric segment, for example ablock copolymeric segment, a gradient copolymeric segment, or a randomcopolymeric segment. The salt-tolerant-enhancing polymeric segment maycomprise repeat units of monomeric residues of one or more polymerizedsalt-tolerant-enhancing monomers, and may optionally have repeat unitsof monomeric residues of one or more polymerized hydrophobic orhydrophilic monomers. In certain embodiments, the repeat units of themonomeric residues of one or more polymerized hydrophobic or hydrophilicmonomers may be present in the salt-tolerant-enhancing polymericsegment. In certain embodiments, the salt-tolerant-enhancing polymericsegment may comprise copolymeric segment of repeat units of monomericresidues of one or more polymerized hydrophobic monomers, and monomericresidues of one or more polymerized salt-tolerant-enhancing monomers.The salt-tolerant star macromolecule of the present invention maycomprise a salt-tolerant-enhancing polymeric segment comprisingcopolymeric segment of repeat units of monomeric residues of one or morepolymerized hydrophilic monomers, and monomeric residues of one or morepolymerized salt-tolerant-enhancing monomers. In certain embodiments,the salt-tolerant-enhancing polymeric segment may comprise a copolymericsegment of repeat units of monomeric residues of one or more polymerizedhydrophilic monomers, monomeric residues of one or more polymerizedhydrophobic monomers, and monomeric residues of one or more polymerizedsalt-tolerant-enhancing monomers.

In certain embodiments, the salt-tolerant-enhancing polymeric segmentmay comprise in the range of between 5-100% of the monomeric residues ofone or more polymerized salt-tolerant-enhancing monomers, for example,between 5-95%, such as between 5-90%; between 5-80%; between 5-75%;between 5-70%; between 5-60%; between 5-50%; between 5-40%; between5-35%; between 5-30%; between 5-25%; between 5-20%; between 5-15%;between 5-10%; between 25-75%; between 50-100%; between 35-65%; orbetween 10-40% of the monomeric residues of one or more polymerizedsalt-tolerant-enhancing monomers. In certain embodiments, asalt-tolerant-enhancing copolymeric arm may comprise more polymerizedmonomeric residues than a hydrophilic polymeric arm, for example, ahydrophilic polymeric polymerized segment of a salt-tolerant-enhancingcopolymeric arm may comprise more polymerized monomeric residues than ahydrophilic polymeric arm.

In an embodiment, the polymer composition, the number of arms on anyparticular star varies across the population of star macromolecules ineach composition, due to the synthetic process used for the synthesis ofthe composition. This process is called “arm first” method and isdescribed in details herein below. Due to variation in the number ofarms in star macromolecules, the number of arms r, s and t are referredas an average number of arms.

As used herein, the term “reference liquid of interest” means the liquidto which the polymer composition will be added. Suitable examples ofreference liquids include, but are not limited to, water, oil or mixturethereof or water with additives which include but are not limited to;surfactants, oils, fats and waxes, emulsifiers, silicone compounds, UVprotectors, antioxidants, various water soluble substances, biogenicagents, and enzyme inhibitors. Such agents are disclosed in U.S. Pat.Nos. 6,663,855 and 7,318,929 and are herein incorporated by reference toprovide definitions for those terms.

Monomer units within the arms may be connected with C—C covalent bonds.This is believed to make them hard to degrade so that the starmacromolecule may perform as efficient thickening agent in a harshenvironment (very high/low pH or in the presence of strong oxidizingagents).

Suitable crosslinkers for the core encompass all of the compounds whichare capable, under the polymerization conditions, of bringing aboutcrosslinking. These include but are not limited di-, tri-,tetra-functional (meth)acrylates, di-, tri- and tetra-functionalstyrenes and other multi- or poly-functional crosslinkers.

Some examples of the crosslinking agents may include but are not limitedto 1,2-divinylbenzene, 1,3-divinylbenzene and 1,4-divinylbenzene,1,2-ethanediol di(meth)acrylate, 1,3-propanediol di(meth)acrylate,1,4-butanediol di(meth)acrylate, 1,5-hexanediol di(meth)acrylate,divinylbenzene, ethyleneglycol di(meth)acrylate, propyleneglycoldi(meth)acrylate, butyleneglycol di(meth)acrylate, triethyleneglycoldi(meth)acrylate, polyethyleneglycol di(meth)acrylate,polypropyleneglycol di(meth)acrylate, polybutyleneglycoldi(meth)acrylate, and allyl(meth)acrylate, glycerol di(meth)acrylate,trimethylolpropane tri(meth)acrylate, pentaerythritoltetra(meth)acrylate, allyl methacrylate, allyl acrylate.

The terms ‘mostly soluble’, ‘not fully soluble’, and ‘not soluble’ areused to describe the extent which a composition which is capable ofbeing dissolved in a reference liquid of interest.

The term ‘mostly soluble’ is used to describe a composition which iscapable dissolves completely with exception of a slight cloudiness inthe reference liquid of interest. The term ‘not fully soluble’ is usedto describe a composition which disperses with a cloudiness in thereference liquid of interest. The term ‘not soluble’ is used to describea composition which does not disperse and remains as a solid in thereference liquid of interest. A list of solvents and non-solvent forpolymers can be found in “Polymer Handbook, 4^(th) Ed.” edited byBrandrup J.; Immergut, Edmund H.; Grulke, Eric A.; Abe, Akihiro; Bloch,Daniel R., John Wiley & Sons: 2005.

An embodiment of the present invention can be exemplified by a multi-armsalt-tolerant star macromolecule wherein the average number of arms inthe star macromolecule is between 5 and 500, preferentially between 10and 250.

In one embodiment, the salt-tolerant star macromolecule has a core whichcontains additional functionality and/or expanded free volume. ‘Expendedfree volume’ of the core is defined as the core with lower crosslinkdensity. The free volume in the core is generated when during thecrosslinking process of crosslinker with monomer P3 and/or with monomerP5, or crosslinker is used. If P3, P5, or crosslinkers, are monomerswith functional groups, these groups will be incorporated in the core.

In one embodiment, the star macromolecule may store and release incontrolled rate the small molecules. ‘Small molecules’ are UV absorbers,minerals, dyes, pigments, solvents, surfactants, metal ions, salts, oroils. These small molecules can be stored inside the core of the starmacromolecule and next released. Each small molecule has some affinityto the core, is soluble in the core environment. Higher affinity of thesmall molecule to the core will result in the lower rate of release fromstar macromolecule. The affinity may be increased or decreased throughnon-covalent forces including ionic, H-bonding, electrostatic,hydrophobic, coordination and metal chelating interactions.

In one embodiment, the star macromolecule displays shear thinningbehavior. ‘Shear thinning’ is defined as is an effect where viscositydecreases with increasing rate of shear stress. The extent of shearthinning behavior is characterized using a Brookfield-type viscometerwhere viscosities are measured under different shear rates.

In one embodiment, the star macromolecule arms comprise a (co)polymersegment that exhibits an upper, or higher, critical solution temperature(UCST or HCST) whereby the star macromolecule is soluble in a liquid athigher temperature, say above 44° C., then at the lower use temperaturethe outer shell polymer segments become insoluble and self assemble toform a shear sensitive gel or in another embodiment the invention theouter shell of the star macromolecule arms comprise a (co)polymersegment that exhibits a lower critical solution temperature (LCST), say5° C., whereby the star macromolecule is soluble in a liquid at lowertemperature then at the use temperature the outer shell polymer segmentsbecome insoluble and self assemble to form a shear sensitive gel. In thecase of a LCST it is envisioned that a copolymer segment with an LCSTbelow 10° C., preferable below 5° C. would be optimal. A non-limitingexample would be a copolymerization of BuMA and DMAEMA and preparationof copolymers with designed LCST. A copolymer with 10% BuMA has a LCSTclose to 0° C. and one would use less BuMA or a less hydrophobic monomersuch as MMA to increase the LCST to ˜5° C. Indeed the Tg of the segmentof the star can be selected to allow dissolution of the star in roomtemperature aqueous media.

In one embodiment, the star macromolecule arms comprise a crosslinkedcore, and arms comprising an water soluble polymeric segment (e.g.poly(acrylic acid), poly(2-hydroxyethyl acrylate),poly(N-isopropylacrylamide), poly(ethylene glycol) methacrylate,quaternized poly(dimethylaminoethyl methacrylate), etc.) and ahydrophobic polymeric segment (e.g. polystyrene or substitutedpolystyrenes, poly(alkyl(meth)acrylate), etc.) or a hydrocarbon-basedsegment. Suitable hydrocarbon-based segments can comprise low molecularweight α-olefin. Lower molecular weight α-olefins are commerciallyavailable and higher molecular weight species can be prepared bytelomerization of ethylene or ethylene propylene mixtures. [Kaneyoshi,H.; Inoue, Y.; Matyjaszewski, K. Macromolecules 2005, 38, 5425-5435.]

Suitable hydrophobic monomers that may be used to form an arm or segmentof an arm, for example a polymeric segment of an arm, such as for P4 (oroptionally within P2), of a star macromolecule may include, but is notlimited to styrene, methyl acrylate, ethyl acrylate, n-butyl acrylate,iso-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, decylacrylate, octyl acrylate; methyl methacrylate; ethyl methacrylate;n-butyl methacrylate; iso-butyl methacrylate; t-butyl methacrylate;2-ethylhexyl methacrylate; decyl methacrylate; methyl ethacrylate; ethylethacrylate; n-butyl ethacrylate; iso-butyl ethacrylate; t-butylethacrylate; 2-ethylhexyl ethacrylate; decyl ethacrylate;2,3-dihydroxypropyl acrylate; 2,3-dihydroxypropyl methacrylate;2-hydroxypropyl acrylate; hydroxypropyl methacrylate; glycidylmethacrylate; glycidyl acrylate, acrylamides, styrene; styreneoptionally substituted with one or more C1-C12 straight or branchedchain alkyl groups; or alkylacrylate. For example, the hydrophobicmonomer may comprise styrene; alpha-methylstyrene; t-butylstyrene;p-methylstyrene; methyl methacrylate; or t-butyl-acrylate. For example,the hydrophobic monomer may comprise styrene. In certain embodiments,the hydrophobic monomer may comprise a protected functional group.

Suitable hydrophilic monomers for that may be used to form an arm orsegment of an arm, for example, a polymeric segment of an arm, such asfor P1, P3, or P5 (or optionally within P2), of a star macromolecule mayinclude, but is not limited to, 2-acrylamido-2-methylpropane sulfonicacid (AMPS), styrene sulphonic acid, protected and unprotected acrylicacids and methacrylic acids including; ethacrylic acid, methyl acrylate,ethyl acrylate, α-butyl acrylate, iso-butyl acrylate, t-butyl acrylate,2-ethylhexyl acrylate, decyl acrylate, octyl acrylate; methylmethacrylate; ethyl methacrylate; n-butyl methacrylate; iso-butylmethacrylate; t-butyl methacrylate; 2-ethylhexyl methacrylate; decylmethacrylate; methyl ethacrylate; ethyl ethacrylate; n-butylethacrylate; iso-butyl ethacrylate; t-butyl ethacrylate; 2-ethylhexylethacrylate; decyl ethacrylate; 2,3-dihydroxypropyl acrylate;2,3-dihydroxypropyl methacrylate; 2-hydroxyethyl acrylate;2-hydroxypropyl acrylate; hydroxypropyl methacrylate; glycerylmonoacrylate; glyceryl monoethacrylate; glycidyl methacrylate; glycidylacrylate; acrylamide; methacrylamide; ethacrylamide; N-methylacrylamide; N,N-dimethyl acrylamide; N,N-dimethyl methacrylamide;N-ethyl acrylamide; N-isopropyl acrylamide; N-butyl acrylamide;N-t-butyl acrylamide; N,N-di-n-butyl acrylamide; N,N-diethylacrylamide;N-octyl acrylamide; N-octadecyl acrylamide; N,N-diethylacrylamide;N-phenyl acrylamide; N-methyl methacrylamide; N-ethyl methacrylamide;N-dodecyl methacrylamide; N,N-dimethylaminoethyl acrylamide; quaternisedN,N-dimethylaminoethyl acrylamide; N,N-dimethylaminoethylmethacrylamide; quaternised N,N-dimethylaminoethyl methacrylamide;N,N-dimethylaminoethyl acrylate; N,N-dimethylaminoethyl methacrylate;quaternised N,N-dimethyl-aminoethyl acrylate; quaternisedN,N-dimethylaminoethyl methacrylate; 2-hydroxyethyl acrylate;2-hydroxyethyl methacrylate; 2-hydroxyethyl ethacrylate; glycerylacrylate; 2-methoxyethyl acrylate; 2-methoxyethyl methacrylate;2-methoxyethyl ethacrylate; 2-ethoxyethyl acrylate; 2-ethoxyethylmethacrylate; 2-ethoxyethyl ethacrylate; maleic acid; maleic anhydrideand its half esters; fumaric acid; itaconic acid; itaconic anhydride andits half esters; crotonic acid; angelic acid; diallyldimethyl ammoniumchloride; vinyl pyrrolidone vinyl imidazole; methyl vinyl ether; methylvinyl ketone; maleimide; vinyl pyridine; vinyl pyridine-N-oxide; vinylfuran; styrene sulphonic acid and its salts; allyl alcohol; allylcitrate; allyl tartrate; vinyl acetate; vinyl alcohol; vinylcaprolactam; vinyl acetamide; or vinyl formamide. For example, thehydrophilic monomer may comprise protected and unprotected acrylic acid,such as methacrylic acid, ethacrylic acid, methyl acrylate, ethylacrylate, α-butyl acrylate, iso-butyl acrylate, t-butyl acrylate,2-ethylhexyl acrylate, decyl acrylate, octyl acrylate; methyl acrylate;methyl methacrylate; methyl ethacrylate; ethyl acrylate; ethylmethacrylate; ethyl ethacrylate; n-butyl acrylate; n-butyl methacrylate;n-butyl ethacrylate; 2-ethylhexyl acrylate; 2-ethylhexyl methacrylate;2-ethylhexyl ethacrylate; N-octyl acrylamide; 2-methoxyethyl acrylate;2-hydroxyethyl acrylate; N,N-dimethylaminoethyl acrylate;N,N-dimethylaminoethyl methacrylate; acrylic acid; methacrylic acid;N-t-butylacrylamide; N-sec-butylacrylamide; N,N-dimethylacrylamide;N,N-dibutylacrylamide; N,N-dihydroxyethyllacrylamide; 2-hydroxyethylacrylate; 2-hydroxyethyl methacrylate; benzyl acrylate;4-butoxycarbonylphenyl acrylate; butyl acrylate; 4-cyanobutyl acrylate;cyclohexyl acrylate; dodecyl acrylate; 2-ethylhexyl acrylate; heptylacrylate; iso-butyl acrylate; 3-methoxybutyl acrylate; 3-methoxypropylacrylate; methyl acrylate; N-butyl acrylamide; N,N-dibutyl acrylamide;ethyl acrylate; methoxyethyl acrylate; hydroxyethyl acrylate; ordiethyleneglycolethyl acrylate. For example, the hydrophilic monomer maycomprise protected and unprotected acrylic acid, such as methacrylicacid, ethacrylic acid, methyl acrylate, ethyl acrylate, α-butylacrylate, iso-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate,decyl acrylate, octyl acrylate; 2-hydroxyethyl acrylate;N-isopropylacrylamide; ethylene glycol methacrylate; (polyethyleneglycol) methacrylate; or quaternized dimethylaminoethyl methacrylate.For example, the hydrophilic monomer may comprise acrylic acid,methacrylic acid, 2-hydroxyethyl acrylate, acrylamide, vinylpyrrolidone, vinyl pyridine, styrene sulphonic acid, PEG-methacrylate,2-(dimethylamino)ethyl methacrylate, 2-(trimethylamino)ethylmethacrylate, 2-acrylamido-2-methylpropane sulphonic acid, acrylic acid,acrylic anhydride, beta-carboxyethyl acrylate, methacrylic acid,4-methacryloxyethyl trimellitic anhydride, 3-methacryloyl-(l)-lysine,o-nitrobenzyl methacrylate, 2-propene-1-sulfonic acid, 2-sulfoethylmethacrylate, trichloroacrylic acid, 4-vinylbenzoic acid, acrylamide/s,2-(N,N-dimethylamino)-ethyl acrylate,N-[2-N,N-dimethylamino)-ethyl]methacrylamide,2-(N,N-dimethylamino)-ethyl methacrylate,3-dimethylaminoneopentylacrylate,N-[3-(N,N-methylamino)-propyl]acrylamide,N-[3-(N,N-Dimethylamino)-propyl]methacrylamide, 2-N-morpholinoethylacrylate, 2-N-morpholinoethyl methacrylate, 3-methacryloyl-(1)-lysine,N,N-diallylamine, diallyldimethyl, 2-aminoethyl methacrylamide,N-(2-aminoethyl) methacrylamide hydrochloride,N-(3-aminopropyl)-methacrylamide hydrochloride,N-(t-BOC-aminopropyl)-acrylamide, 2-(t-butylamino)ethyl methacrylate,2-(N,N-diethylamino)-ethyl methacrylate (DEAEMA),2-diisopropylaminoethyl methacrylate. For example, the hydrophilicmonomer may comprise acrylic acid.

Suitable salt-tolerant-enhancing monomers for P2 that may be used toform a salt-tolerant-enhancing segment may include, but are not limitedto, monomers having an ionizable functional group, an anionic functionalgroup, a cationic functional group, or a hydrogen-bonding capablefunctional group, such as a hydrogen bond donating functional group or ahydrogen bond accepting functional group. For example, suitablesalt-tolerant-enhancing monomers may include, but is not limited to,protected and unprotected acrylic acid, methacrylic acid, ethacrylicacid, methyl acrylate, ethyl acrylate, α-butyl acrylate, iso-butylacrylate, t-butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, octylacrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate,iso-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate,decyl methacrylate, methyl ethacrylate, ethyl ethacrylate, n-butylethacrylate, iso-butyl ethacrylate, t-butyl ethacrylate, 2-ethylhexylethacrylate, decyl ethacrylate, 2,3-dihydroxypropyl acrylate,2,3-dihydroxypropyl methacrylate, 2-hydroxyethyl acrylate,2-hydroxypropyl acrylate, hydroxypropyl methacrylate, glycerylmonoacrylate, glyceryl monoethacrylate, glycidyl methacrylate, glycidylacrylate, acrylamide, methacrylamide, ethacrylamide, N-methylacrylamide, N,N-dimethyl acrylamide, N,N-dimethyl methacrylamide,N-ethyl acrylamide, N-isopropyl acrylamide, N-butyl acrylamide,N-t-butyl acrylamide, N,N-di-n-butyl acrylamide, N,N-diethylacrylamide,N-octyl acrylamide, N-octadecyl acrylamide, N,N-diethylacrylamide,N-phenyl acrylamide, N-methyl methacrylamide, N-ethyl methacrylamide,N-dodecyl methacrylamide, N,N-dimethylaminoethyl acrylamide, quaternisedN,N-dimethylaminoethyl acrylamide, N,N-dimethylaminoethylmethacrylamide, quaternised N,N-dimethylaminoethyl methacrylamide,N,N-dimethylaminoethyl acrylate, N,N-dimethylaminoethyl methacrylate,quaternised N,N-dimethyl-aminoethyl acrylate, quaternisedN,N-dimethylaminoethyl methacrylate, 2-hydroxyethyl methacrylate,2-hydroxyethyl ethacrylate, glyceryl acrylate, 2-methoxyethyl acrylate,2-methoxyethyl methacrylate, 2-methoxyethyl ethacrylate, 2-ethoxyethylacrylate, 2-ethoxyethyl methacrylate, 2-ethoxyethyl ethacrylate, maleicacid, maleic anhydride and its half esters, fumaric acid, itaconic acid,itaconic anhydride and its half esters, crotonic acid, angelic acid,diallyldimethyl ammonium chloride, vinyl pyrrolidone vinyl imidazole,methyl vinyl ether, methyl vinyl ketone, maleimide, vinyl pyridine,vinyl pyridine-N-oxide, vinyl furan, styrene sulphonic acid and itssalts, allyl alcohol, allyl citrate, allyl tartrate, vinyl acetate,vinyl alcohol, vinyl caprolactam, vinyl acetamide, vinyl formamide,allyl heptafluorobutyrate, allyl heptafluoroisopropyl ether, allyl1H,1H-pentadecafluorooctyl ether, allylpentafluorobenzene, allylperfluoroheptanoate, allyl perfluorononanoate, allyl perfluorooctanoate,allyl tetrafluoroethyl ether, allyl trifluoroacetate,bis(hexafluoroisopropyl) itaconate, bis(hexafluoroisopropyl) maleate,bis(perfluorooctyl)itaconate, bis(perfluorooctyl)maleate,bis(trifluoroethyl) itaconate, bis(2,2,2-trifluoroethyl) maleate,2-(N-butylperfluorooctanesulfamido) ethyl acrylate,trihydroperfluoroheptyl acrylate, trihydroperfluoroheptyl methacrylate,trihydroperfluoroundecyl acrylate, trihydroperfluoroundecylmethacrylate, epifluorohydrin, 2-(N-ethylperfluorooctane sulfamido)ethyl acrylate, 2-(N-ethylperfluorooctane sulfamido) ethyl methacrylate,2-fluoroethyl acrylate, 2-fluoroethyl methacrylate, m-fluorostyrene,o-fluorostyrene, p-fluorostyrene, tetrahydroperfluorodecyl acrylate,tetrahydroperfluorodecyl methacrylate, 1H,1H-heptafluorobutylacrylamide,heptafluorobutyl acrylate, 1H,1H-heptafluorobutylmethacrylamide,2-N-heptafluorobutyrylamino-4,6-dichlorotriazine,1H,1H-heptafluoro-n-butyl methacrylate, 1H,1H,9H-hexadecafluorononylacrylate, 1H,1H,9H-hexadecafluorononyl methacrylate, hexafluorobisphenol A diacrylate, hexafluoro bisphenol A dimethacrylate,2,2,3,4,4,4-hexafluorobutyl acrylate, 2,2,3,4,4,4-hexafluorobutylmethacrylate, hexafluoroisopropyl acrylate, mono-hexafluoroisopropylmaleate, hexafluoroisopropyl urethane of isocyanatoethyl methacrylate,2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol diacrylate,2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol dimethacrylate,1H,1H,5H-octafluoropentyl acrylate, 1H,1H,5H-octafluoropentylmethacrylate, pentafluorobenzyl acrylate, pentafluorobenzylmethacrylate, pentafluorophenyl acrylate, pentafluorophenylmethacrylate, 2,2,3,3,3-pentafluoropropyl acrylate,2,2,3,3,3-pentafluoropropyl methacrylate, pentafluorostyrene,perfluorocyclohexyl-1,4-dimethyl dimethacrylate, perfluorocyclohexylmethyl acrylate, perfluorocyclohexylmethyl methacrylate,perfluorocyclopentene, perfluoroheptoxypoly(propyloxy) acrylate,perfluoroheptoxypoly-(propyloxy) methacrylate,perfluorooctoxy-poly(iso-butoxy)-2-chloropropoxy-1,2-propyl diacrylate,mono-perfluorooctyl maleate, mono-perfluorooctyl itaconate,perfluorooctyl acrylate, 1H,1H-perfluorooctyl acrylate,1H,1H-perfluorooctyl methacrylate, polyperfluoroethylene glycoldiacrylate, polyperfluoroethylene glycol dimethacrylate,2,2,3,3-tetrafluoro-1,4-butanediol diacrylate,2,2,3,3-tetrafluoro-1,4-butanediol dimethacrylate,2,2,3,3-tetrafluoropropyl acrylate, 2,2,3,3-tetrafluoropropylmethacrylate, 1,1,5,5-tetrahydroperfluoro-1,5-pentanedioldimethacrylate, trifluoroethyl acid itaconate, mono-trifluoroethyl acidmaleate, 2,2,2-trifluoroethyl acrylate, 2,2,2-trifluoroethylmethacrylate, 3-(trifluoromethyl) benzyl acrylate, 3-(trifluoromethyl)benzyl methacrylate, 1-(trifluoromethyl) vinyl acetate, 4-vinylbenzylhexafluoroisopropyl ether, 4-vinylbenzyl perfluorooctanoate,4-vinylbenzyl trifluoroacetate, vinyl heptafluorobutyrate, vinylperfluoroheptanoate, vinyl perfluorononanoate, vinyl perfluorooctanoate,vinyl trifluoroacetate, hexafluoroisopropyl itaconate,hexafluoroisopropyl methacrylate,tridecafluoro-1,1,2,2-tetrahydrooctyl-1,1-methyl dimethoxy silane,tridecafluoro-1,1,2,2-Tetrahydrooctyl-1-dimethyl methoxy silane andmixtures thereof.

Even more preferred salt-tolerant-enhancing monomers are those selectedfrom methyl acrylate, methyl methacrylate, methyl ethacrylate, ethylacrylate, ethyl methacrylate, ethyl ethacrylate, n-butyl acrylate,n-butyl methacrylate, n-butyl ethacrylate, 2-ethylhexyl acrylate,2-ethylhexyl methacrylate, 2-ethylhexyl ethacrylate, N-octyl acrylamide,2-methoxyethyl acrylate, 2-hydroxyethyl acrylate, N,N-dimethylaminoethylacrylate, N,N-dimethylaminoethyl methacrylate, acrylic acid, methacrylicacid, N-t-butylacrylamide, N-sec-butylacrylamide,N,N-dimethylacrylamide, N,N-dibutylacrylamide,N,N-dihydroxyethyllacrylamide 2-hydroxyethyl acrylate, 2-hydroxyethylmethacrylate, benzyl acrylate, 4-butoxycarbonylphenyl acrylate, butylacrylate, 4-cyanobutyl acrylate, cyclohexyl acrylate, dodecyl acrylate,2-ethylhexyl acrylate, heptyl acrylate, iso-butyl acrylate,3-methoxybutyl acrylate, 3-methoxypropyl acrylate, methyl acrylate,N-butyl acrylamide, N,N-dibutyl acrylamide, ethyl acrylate, methoxyethylacrylate, hydroxyethyl acrylate, diethyleneglycolethyl acrylate, styrene(optionally substituted with one or more C1-C12 straight or branchedchain alkyl groups), alpha-methylstyrene, t-butylstyrene,p-methylstyrene, 2-fluoroethyl acrylate, 2-fluoroethyl methacrylate,m-fluorostyrene, o-fluorostyrene, p-fluorostyrene, and mixtures thereof.

Suitable monomers that may be used to form a core of a salt-tolerantstar macromolecule may include, but are not limited to, amultifunctional monomer, for example, a hexafunctional monomer, apentafunctional monomer, a tetrafunctional monomer, a trifunctionalmonomer, or a difunctional monomer. For example, a crosslinker may be ahydrophobic monomer or a hydrophilic monomer, such as a hydrophobicmultifunctional monomer or a hydrophilic multifunctional monomer, forexample, a hydrophobic difunctional monomer or a hydrophilicdifunctional monomer. For example, the crosslinker may be a hydrophobiccrosslinker, including, but not limited to, 1,2-divinylbenzene;1,3-divinylbenzene; 1,4-divinylbenzene; 1,2-ethanediol di(meth)acrylate;1,3-propanediol di(meth)acrylate; 1,4butanediol di(meth)acrylate;1,5-hexanediol di(meth)acrylate; divinylbenzene; ethyleneglycoldi(meth)acrylate; di(ethylene glycol)diacrylate (DEGlyDA);propyleneglycol di(meth)acrylate; butyleneglycol di(meth)acrylate;triethyleneglycol di(meth)acrylate; polyethyleneglycol di(meth)acrylate;polypropyleneglycol di(meth)acrylate; polybutyleneglycoldi(meth)acrylate; allyl(meth)acrylate; glycerol di(meth)acrylate;trimethylolpropane tri(meth)acrylate; pentaerythritoltetra(meth)acrylate; allyl methacrylate; or allyl acrylate. For example,the crosslinker may be di(ethylene glycol)diacrylate (DEGlyDA) ordivinylbenzene. For example, the crosslinker may be divinylbenzene.

Suitable salt-tolerant star macromolecules may include, but are notlimited to, a mikto star macromolecule, a water-soluble starmacromolecule, a gel-forming star macromolecule, emulsifier/thickeningagent star macromolecules, fracking fluid thickening starmacromolecules, fracking fluid gelling star macromolecules, orcombinations thereof. In certain embodiments, the star macromolecule mayhave a molecular weight of greater than 5,000 g/mol, for example,between 5,000 g/mol and 10,000,000 g/mol, such as between 25,000 g/moland 7,000,000 g/mol; between 50,000 g/mol and 5,000,000 g/mol; 20,000g/mol and 1,000,000 g/mol; between 100,000 g/mol and 2,500,000 g/mol;between 125,000 g/mol and 1,750,000 g/mol; between 150,000 g/mol and1,750,000 g/mol; between 200,000 g/mol and 1,500,000 g/mol; between225,000 g/mol and 1,250,000 g/mol; between 125,000 g/mol and 1,000,000g/mol; between 125,000 g/mol and 900,000 g/mol; between 125,000 g/moland 800,000 g/mol; between 125,000 g/mol and 700,000 g/mol; between150,000 g/mol and 650,000 g/mol; between 200,000 g/mol and 500,000g/mol; between 200,000 g/mol and 600,000 g/mol; between 225,000 g/moland 650,000 g/mol; between 250,000 g/mol and 550,000 g/mol; between350,000 g/mol and 500,000 g/mol; between 300,000 g/mol and 500,000g/mol; or between 350,000 g/mol and 750,000 g/mol.

Star macromolecules with a single peak in the GPC curve with apolydispersity index (PDI) above 1.0 and below 3.5 are preferred.Suitable salt-tolerant star macromolecules may have a polydispersityindex (PDI) of less than 3.0, for example, a PDI of less than 2.5, suchas less than 2.0 or less than 1.7. For example, a star macromolecule mayhave a PDI of between 1.0 to 3.0, such as between 1.0 and 2.7; between1.0 and 2.5; between 1.5 and 2.4; between 1.0 and 1.9; between 1.0 and1.8; between 1.0 and 1.7; between 1.0 and 1.6; between 1.0 and 1.5;between 1.0 and 1.4; between 1.0 and 1.3; between 1.0 and 1.2; between1.0 and 1.1; between 1.05 and 1.75; between 1.1 and 1.7; between 1.15and 1.65; between 1.15 and 1.55; between 1.7 and 2.3.

Suitable salt-tolerant star macromolecules may comprise arms that are ofthe same type or a different type and are homopolymeric, copolymeric,comprise multiple block segment, random segments, gradient segments orno particular segments. In certain embodiments, the star macromoleculemay comprise, for example, one or more arm-types, such as, two or more,three or more, four or more, or five or more arm-types. Suitable armtypes may include, but are not limited to, homopolymeric arms,copolymeric arms, such as random copolymeric arms or block copolymericarms, or combinations thereof. For example, a star macromolecule maycomprise homopolymeric arms and copolymeric arms, such as blockcopolymeric arms. Suitable arm types may also include, but are notlimited to, salt-tolerant-enhancing arms, hydrophilic arms, hydrophobicarms, or amphiphilic arms. In certain embodiments, a star macromoleculearm may comprise hydrophilic polymeric segments comprising hydrophilicmonomeric residues, salt-tolerant-enhancing segments comprisingsalt-tolerant-enhancing monomeric residues, hydrophobic polymericsegments comprising hydrophobic monomeric residues, amphiphilicpolymeric segments comprising amphiphilic monomeric residues, orcombinations thereof. For example, in certain embodiments, a starmacromolecule may comprise homopolymeric arms and copolymeric arms, suchas hydrophilic homopolymeric arms, copolymeric arms comprisinghydrophilic polymeric segments and salt-tolerant-enhancing polymericsegments, and copolymeric arms comprising hydrophilic polymeric segmentsand hydrophobic polymeric segments.

Suitable salt-tolerant star macromolecules may comprise hydrophilicpolymeric segments, such as P1, P3, or P5, which may comprise ahydrophilic homopolymeric segment or a hydrophilic copolymeric segmentcomprising repeat units of monomeric residues of one or more, such astwo or more, polymerized hydrophilic monomers, for example, ahydrophilic segment block copolymeric segment, a hydrophilic gradientcopolymeric segment, or a hydrophilic random copolymeric segment.

Suitable salt-tolerant star macromolecules may comprisesalt-tolerant-enhancing polymeric segments, such as P2, which maycomprise a salt-tolerant-enhancing homopolymerized segment or asalt-tolerant-enhancing copolymerized segment comprising repeat units ofmonomeric residues of one or more, such as two or more, polymerizedsalt-tolerant-enhancing monomers, and optionally, monomeric residues ofone or more, such as two or more, polymerized hydrophobic or hydrophilicmonomers. The salt-tolerant-enhancing copolymerized segment may be asalt-tolerant-enhancing segment block copolymeric segment, asalt-tolerant-enhancing gradient copolymeric segment, or asalt-tolerant-enhancing random copolymeric segment. In certainembodiments, the monomeric residues of the one or more, or two or more,polymerized hydrophobic or hydrophilic monomers are present in thesalt-tolerant-enhancing copolymeric segment. For example, thesalt-tolerant-enhancing copolymerized segment may be block, gradient, orrandom copolymeric segment comprising repeat units of monomeric residuesof one or more, such as two or more, polymerized salt-tolerant-enhancingmonomers, and monomeric residues of one or more, such as two or more,polymerized hydrophobic monomers. For example, thesalt-tolerant-enhancing copolymerized segment may be block, gradient, orrandom copolymeric segment comprising repeat units of monomeric residuesof one or more, such as two or more, polymerized salt-tolerant-enhancingmonomers, and monomeric residues of one or more, such as two or more,polymerized hydrophilic monomers. In certain embodiments, thesalt-tolerant-enhancing copolymerized segment may be block, gradient, orrandom copolymeric segment comprising repeat units of monomeric residuesof one or more, such as two or more, polymerized salt-tolerant-enhancingmonomers, and monomeric residues of one or more, such as two or more,polymerized hydrophobic monomers, and monomeric residues of one or more,such as two or more, polymerized hydrophilic monomers.

Suitable salt-tolerant star macromolecules may comprise hydrophobicpolymeric segments, such as P4, which may comprise a hydrophobichomopolymeric segment or a hydrophobic copolymeric segment comprisingrepeat units of monomeric residues of one or more, such as two or more,polymerized hydrophobic monomers, for example, a hydrophobic segmentblock copolymeric segment, a hydrophobic gradient copolymeric segment,or a hydrophobic random copolymeric segment.

Suitable salt-tolerant star macromolecules may also comprise arms thatare covalently linked to the core of the star macromolecule. In certainembodiments, the arms of a star macromolecule may be covalently linkedto the core of the star macromolecule via crosslinking, such ascrosslinking with a crosslinker, for example, a hydrophobic difunctionalcrosslinker or a hydrophilic difunctional crosslinker. For example, armsof a star macromolecule, such as homopolymeric arms and blockcopolymeric arms of a mikto star macromolecule, may be covalently linkedtogether to form a core by crosslinking an end of the arms with acrosslinker, such as with a hydrophobic difunctional crosslinker or ahydrophilic difunctional crosslinker.

Suitable salt-tolerant star macromolecules may also comprise arms ofvarying length and/or degree of polymerization. In certain embodiments,for example, a star macromolecule may comprise homopolymeric arms andblock copolymeric arms, wherein the homopolymeric arms of a shorterlength and/or a lesser degree of polymerization in relation to the blockcopolymeric arms. In certain embodiments, for example, a starmacromolecule may comprise homopolymeric arms and block copolymericarms, wherein the block copolymeric arms of a longer length and/or agreater degree of polymerization in relation to the homopolymeric arms.In certain embodiments, a star macromolecule may comprise hydrophilichomopolymeric arms and block copolymeric arms, comprising (i)hydrophobic polymeric segments distal to the star core and hydrophilicpolymeric segments that are proximal to the core of the star, wherein adistal portion of the hydrophobic polymeric segments of the copolymericarm extends beyond a distal portion of the hydrophilic homopolymericarms, and (ii) salt-tolerant-enhancing polymeric segments distal to thestar core and hydrophilic polymeric segments that are proximal to thecore of the star, wherein a distal portion of thesalt-tolerant-enhancing polymeric segments of the copolymeric armextends beyond a distal portion of the hydrophilic homopolymeric arms.For example, a star macromolecule may comprise hydrophilic homopolymericarms comprising polymerized hydrophilic monomeric residues and blockcopolymeric arms comprising (i) hydrophobic polymeric segments distal tothe core of the star and hydrophilic polymeric segments that areproximal to the core of the star, wherein the distal hydrophobicpolymeric segments extend beyond the most distal portion, in relation tothe core, of the hydrophilic homopolymeric arms, and/or wherein a distalportion of the proximal hydrophilic polymeric segments of thecopolymeric arm extend beyond the most distal portion, in relation tothe core, of the hydrophilic homopolymeric arms, (ii)salt-tolerant-enhancing polymeric segments distal to the core of thestar and hydrophilic polymeric segments that are proximal to the core ofthe star, wherein the distal salt-tolerant-enhancing polymeric segmentsextend beyond the most distal portion, in relation to the core, of thehydrophilic homopolymeric arms, and/or wherein a distal portion of theproximal hydrophilic polymeric segments of the copolymeric arm extendbeyond the most distal portion, in relation to the core, of thehydrophilic homopolymeric arms.

In certain embodiments, a star macromolecule may comprise hydrophilichomopolymeric arms and block copolymeric arms, comprising (i)hydrophobic polymeric segments distal to the star core and hydrophilicpolymeric segments that are proximal to the star core, wherein thedegree of polymerization of the hydrophilic polymeric segments of thecopolymeric arms are greater than, for example, greater than 20%, suchas between 30% to 300%, between 40% to 250%, between 50% to 200%,between 75% to 250%, or between 100% to 500%, the degree ofpolymerization of the hydrophilic homopolymeric arms, such that a distalportion of the hydrophilic polymeric segments of the copolymeric armextends beyond the a distal portion of the hydrophilic homopolymericarms, and (ii) salt-tolerant-enhancing polymeric segments distal to thestar core and hydrophilic polymeric segments that are proximal to thestar core, wherein the degree of polymerization of the hydrophilicpolymeric segments of the copolymeric arms are greater than, forexample, greater than 20%, such as between 30% to 300%, between 40% to250%, between 50% to 200%, between 75% to 250%, or between 100% to 500%,the degree of polymerization of the hydrophilic homopolymeric arms, suchthat a distal portion of the hydrophilic polymeric segments of thecopolymeric arms extends beyond the a distal portion of the hydrophilichomopolymeric arms.

In certain embodiments, suitable salt-tolerant star macromolecules maycomprise hydrophilic homopolymeric arms comprising polymerizedhydrophilic monomeric residues and block copolymeric arms comprising (i)hydrophobic polymeric segments distal to the core of the star andhydrophilic polymeric segments proximal to the core of the star, (ii)salt-tolerant-enhancing polymeric segments distal to the core of thestar and hydrophilic polymeric segments proximal to the core of thestar, wherein the polymerized hydrophilic monomeric residues of thehomopolymeric arm and the hydrophilic polymeric segments of thecopolymeric arms may be derived from the same hydrophilic monomers, andmay have the same or different degree of polymerization, for example, adegree of polymerization of between 10 to 2000 monomeric residues, suchas, between 50 to 500 monomeric residues; between 50 to 400 monomericresidues; between 50 to 300 monomeric residues; between 50 to 200monomeric residues; between 100 to 250 monomeric residues; between 125to 175 monomeric residues; or between 150 to 300 monomeric residues. Forexample, a star macromolecule may comprise hydrophilic homopolymericarms comprising polymerized hydrophilic monomeric residues and blockcopolymeric arms comprising (i) hydrophobic polymeric segments distal tothe core of the star and hydrophilic polymeric segments proximal to thecore of the star, (ii) salt-tolerant-enhancing polymeric segments distalto the core of the star and hydrophilic polymeric segments proximal tothe core of the star, wherein the polymerized hydrophilic monomericresidues of the homopolymeric arm and the hydrophilic polymeric segmentsof the copolymeric arms may be derived from the same hydrophilicmonomers, and may have the same degree of polymerization, and whereinthe hydrophobic polymeric segments of the copolymeric arms may have adegree of polymerization of between 1 to 500 monomeric residues, such asbetween 1 to 450 monomeric residues; between 1 to 400 monomericresidues; between 1 to 350 monomeric residues; between 10 to 425monomeric residues; between 20 to 250 monomeric residues; between 30 to200 monomeric residues; between 50 to 200 monomeric residues; between 1to 60 monomeric residues; between 1 to 50 monomeric residues; between 1to 45 monomeric residues; between 5 to 40 monomeric residues; between 8to 35 monomeric residues; between 10 to 30 monomeric residues; between12 to 25 monomeric residues; between 14 to 22 monomeric residues;between 15 to 30 monomeric residues; or between 5 to 20 monomericresidues, and wherein the salt-tolerant-enhancing polymeric segments ofthe copolymeric arms may have a degree of polymerization of between 1 to500 monomeric residues, such as between 1 to 450 monomeric residues;between 1 to 400 monomeric residues; between 1 to 350 monomericresidues; between 10 to 425 monomeric residues; between 20 to 250monomeric residues; between 30 to 200 monomeric residues; between 50 to200 monomeric residues; between 1 to 60 monomeric residues; between 1 to50 monomeric residues; between 1 to 45 monomeric residues; between 5 to40 monomeric residues; between 8 to 35 monomeric residues; between 10 to30 monomeric residues; between 12 to 25 monomeric residues; between 14to 22 monomeric residues; between 15 to 30 monomeric residues; orbetween 5 to 20 monomeric residues.

In certain embodiments, suitable salt-tolerant star macromolecules maycomprise hydrophilic polymeric arms comprising repeat units ofpolymerized hydrophilic monomeric residues having a degree ofpolymerization of the monomeric residues, represented by q1, having avalue between 10 to 2000, such as, between 50 to 500; between 50 to 400;between 50 to 300; between 50 to 200; between 100 to 250; between 125 to175; or between 150 to 300.

In certain embodiments, suitable salt-tolerant star macromolecules maycomprise salt-tolerant-enhancing copolymeric arms comprising repeatunits of polymerized salt-tolerant-enhancing monomeric residues having adegree of polymerization of the monomeric residues, represented by q2,having a value between 10 to 500, such as, between 10 to 400; between 10to 300; between 10 to 200; between 10 to 100; between 10 to 75; between10 to 50; between 10 to 40; between 10 to 30; between 10 to 20; between10 to 15; between 15 to 25; between 20 to 30; between 20 to 40; between20 to 50; between 17 to 33; or between 13 to 23.

In certain embodiments, suitable salt-tolerant star macromolecules maycomprise salt-tolerant-enhancing copolymeric arms comprising repeatunits of polymerized hydrophilic monomeric residues having a degree ofpolymerization of the monomeric residues, represented by q3, having avalue between 10 to 2000, such as, between 50 to 500; between 50 to 400;between 50 to 300; between 50 to 200; between 100 to 250; between 125 to175; or between 150 to 300.

In certain embodiments, suitable salt-tolerant star macromolecules maycomprise hydrophobic copolymeric arms comprising repeat units ofpolymerized hydrophobic monomeric residues having a degree ofpolymerization of the monomeric residues, represented by q4, having avalue between 10 to 500, such as, between 10 to 400; between 10 to 300;between 10 to 200; between 10 to 100; between 10 to 75; between 10 to50; between 10 to 40; between 10 to 30; between 10 to 20; between 10 to15; between 15 to 25; between 20 to 30; between 20 to 40; between 20 to50; between 17 to 33; or between 13 to 23.

In certain embodiments, suitable salt-tolerant star macromolecules maycomprise hydrophobic copolymeric arms comprising repeat units ofpolymerized hydrophilic monomeric residues having a degree ofpolymerization of the monomeric residues, represented by q5, having avalue between 10 to 2000, such as, between 50 to 500; between 50 to 400;between 50 to 300; between 50 to 200; between 100 to 250; between 125 to175; or between 150 to 300.

Suitable salt-tolerant star macromolecules may have a wide range oftotal number of arms, for example, a star macromolecule may comprisegreater than 5 arms. For example, a suitable star macromolecule maycomprise between 5 and 500 arms, such as between 10 and 400 arms;between 12 and 300 arms; between 14 and 200 arms; between 14 and 150arms; between 15 and 100 arms; between 15 and 90 arms; between 15 and 80arms; between 15 and 70 arms; between 15 and 60 arms; between 15 and 50arms; between 20 and 50 arms; between 25 and 45 arms; between 25 and 35arms; between 30 and 45 arms; or between 30 and 50 arms.

Suitable salt-tolerant star macromolecules may have more than one armtype, such as two or more different arm types, where in a molar ratio ofthe different arm types may be between 40:1 and 1:1. For example, a starmacromolecule comprising two different arm types, such as ahomopolymeric arm, for example, a hydrophilic homopolymeric arm, and acopolymeric arm, for example, a copolymeric arm comprising hydrophilicpolymeric segments and hydrophobic polymeric segments, may have a molarratio of the two different arm types between 40:1 to 2:1, such asbetween 35:1 to 2:1; between 30:1 to 2:1; between 25:1 to 2:1; between20:1 to 2:1; between 15:1 to 2:1; between 10:1 to 2:1; between 9:1 to2:1; between 8:1 to 2:1; between 7:1 to 2:1; between 7:3 to 2:1; between7:5 to 2:1; between 4:5 to 2:1; between 6:1 to 2:1; between 5:1 to 2:1;between 4:1 to 2:1; between 3:1 to 2:1; between 2:1 to 1:1; between 8:1to 3:1; between 7:1 to 2:1; or between 5:1 to 3:1, and a copolymeric armcomprising hydrophilic polymeric segments and salt-tolerant-enhancingpolymeric segments, may have a molar ratio of the two different armtypes between 40:1 to 2:1, such as between 35:1 to 2:1; between 30:1 to2:1; between 25:1 to 2:1; between 20:1 to 2:1; between 15:1 to 2:1;between 10:1 to 2:1; between 9:1 to 2:1; between 8:1 to 2:1; between 7:1to 2:1; between 7:3 to 2:1; between 7:5 to 2:1; between 4:5 to 2:1;between 6:1 to 2:1; between 5:1 to 2:1; between 4:1 to 2:1; between 3:1to 2:1; between 2:1 to 1:1; between 8:1 to 3:1; between 7:1 to 2:1; orbetween 5:1 to 3:1. For example, a star macromolecule comprising threedifferent arm types, such as a homopolymeric arm, for example, ahydrophilic homopolymeric arm, and a first copolymeric arm, for example,a copolymeric arm comprising hydrophilic polymeric segments andhydrophobic polymeric segments, and a second copolymeric arm comprisinghydrophilic polymeric segments and salt-tolerant-enhancing polymericsegments, may have a molar ratio of homopolymeric arms to the twocopolymeric arms types between 40:1 to 2:1, such as between 35:1 to 2:1;between 30:1 to 2:1; between 25:1 to 2:1; between 20:1 to 2:1; between15:1 to 2:1; between 10:1 to 2:1; between 9:1 to 2:1; between 8:1 to2:1; between 7:1 to 2:1; between 7:3 to 2:1; between 7:5 to 2:1; between4:5 to 2:1; between 6:1 to 2:1; between 5:1 to 2:1; between 4:1 to 2:1;between 3:1 to 2:1; between 2:1 to 1:1; between 8:1 to 3:1; between 7:1to 2:1; or between 5:1 to 3:1.

Suitable salt-tolerant star macromolecules may be represented by theFormula Z, wherein the star macromolecule may have a sum total number ofarms (r+s+t) of between 3 and 500, such as between 5 and 450; between 8and 400; between 10 and 300; between 12 and 350; between 14 and 300;between 15 and 250; between 16 and 200; between 5 and 150; between 5 and100; between 5 and 100; between 5 and 50; between 5 and 25; between 10and 75; between 15 and 45; between 15 and 30; or between 20 and 40.

Suitable salt-tolerant star macromolecules may be represented by theFormula Z, wherein the star macromolecule may have a total number ofhydrophilic polymeric arms, such as hydrophilic homopolymeric arms orhydrophilic copolymeric arms, covalently attached to the core,represented by r having a value of 0 to 1000, such as between 2 and 500;between 3 and 300; between 4 and 200; between 5 and 150; between 6 and100; between 7 and 75; between 8 and 50; between 9 and 40; between 10and 30; between 15 and 45; between 20 and 30; between 25 and 50; between50 and 100; between 75 and 125; between 10 and 75; between 15 and 45;between 15 and 30; or between 20 and 40.

Suitable salt-tolerant star macromolecules may be represented by theFormula Z, wherein the star macromolecule may have a total number ofsalt-tolerant-enhancing copolymeric arms covalently attached to thecore, independently represented by s having a value of between 1 and1000, such as between 2 and 500; between 3 and 250; between 4 and 200;between 5 and 150; between 6 and 100; between 7 and 75; between 8 and50; between 9 and 40; between 10 and 30; between 15 and 45; between 20and 30; between 25 and 50; between 50 and 100; between 75 and 125;between 10 and 75; between 15 and 45; between 15 and 30; between 20 and40; between 2 and 50; between 2 and 40; between 2 and 30; between 2 and25; between 3 and 20; between 4 and 15; between 1 and 10; between 1 and8; between 1 and 6; or between 2 and 5.

Suitable salt-tolerant star macromolecules may be represented by theFormula Z, wherein the star macromolecule may have a total number ofhydrophobic copolymeric arms covalently attached to the core,represented by t having a value of 0 to 1000, such as between 2 and 500;between 3 and 300; between 4 and 200; between 5 and 150; between 6 and100; between 7 and 75; between 8 and 50; between 9 and 40; between 10and 30; between 15 and 45; between 20 and 30; between 25 and 50; between50 and 100; between 75 and 125; between 10 and 75; between 15 and 45;between 15 and 30; between 20 and 40; between 2 and 50; between 2 and40; between 2 and 30; between 2 and 25; between 3 and 20; between 4 and15; between 1 and 10; between 1 and 8; between 1 and 6; or between 2 and5.

Suitable salt-tolerant star macromolecules may be represented by theFormula Z, wherein the star macromolecule may have a total number ofsalt-tolerant-enhancing arms types covalently attached to the core,represented by n having a value of at least 1, such as between 1 to 10;between 2 and 9; between 3 and 8; between 4 and 7; between 5 and 10;between 2 and 7; or between 1 and 5.

Suitable salt-tolerant star macromolecules may include, but is notlimited to, comprising arms having a molecular weight of greater than1,000 g/mol. For example, a star macromolecule may comprise arms havinga molecular weight of between 1,000 g/mol and 400,000 g/mol, such asbetween 2,000 g/mol and 300,000 g/mol; 5,000 g/mol and 200,000 g/mol;5,000 g/mol and 100,000 g/mol; 5,000 g/mol and 75,000 g/mol; 5,000 g/moland 60,000 g/mol; 5,000 g/mol and 50,000 g/mol; 10,000 g/mol and 100,000g/mol; 10,000 g/mol and 150,000 g/mol; between 10,000 g/mol and 125,000g/mol; between 10,000 g/mol and 100,000 g/mol; between 10,000 g/mol and90,000 g/mol; between 10,000 g/mol and 80,000 g/mol; between 10,000g/mol and 70,000 g/mol; between 50,000 g/mol and 60,000 g/mol; between50,000 g/mol and 70,000 g/mol; between 10,000 g/mol and 40,000 g/mol;between 10,000 g/mol and 30,000 g/mol; between 10,000 g/mol and 20,000g/mol; between 20,000 g/mol and 175,000 g/mol; between 20,000 g/mol and100,000 g/mol; between 20,000 g/mol and 75,000 g/mol; between 20,000g/mol and 50,000 g/mol; between 15,000 g/mol and 45,000 g/mol; orbetween 15,000 g/mol and 30,000 g/mol.

Suitable arms of a salt-tolerant star macromolecule may include, but isnot limited to, arms having an HLB value of at least 17 (wherein the HLBis calculated per the formula set forth in the test procedures). Forexample, suitable arms of a star macromolecule may have an HLB value ofgreater than 17.25, such as greater than 18.5; at least 19; between 17.5to 20; between 17.5 to 19.5; between 18 to 20; between 18.5 to 20;between 19 to 20; between 19.5 to 20; between 18 to 19.5; between 18.5to 19.75; between 18.2 to 19.2; or between 18.75 to 19.5.

Suitable hydrophobic polymeric segments of a copolymeric arm of asalt-tolerant star macromolecule may include, but is not limited to,hydrophobic polymeric segments having an HLB value of less than 8. Forexample, suitable hydrophobic polymeric segments may have an HLB valueof less than 7, such as less than 6; less than 5; less than 4; less than3; less than 2; or about 1.

Suitable arms of a salt-tolerant star macromolecule may include, but isnot limited to, arms having a polydispersity index (PDI) value of lessthan 3.0. For example, suitable arms of a star macromolecule may havePDI value of less than 2.5, such as less that 2.25; less that 2.0; lessthan 1.7; between 1.0 to 3.0, such as between 1.0 and 2.5; between 1.0and 2.3; between 1.0 and 2.0; between 1.0 and 1.9; between 1.0 and 1.8;between 1.0 and 1.7; between 1.0 and 1.6; between 1.0 and 1.5; between1.0 and 1.4; between 1.0 and 1.3; between 1.0 and 1.2; between 1.0 and1.1; between 1.05 and 1.75; between 1.1 and 1.7; between 1.15 and 1.65;or between 1.15 and 1.55.

Suitable cores of a salt-tolerant star macromolecule may be formed by orderived from, but is not limited to, crosslinking of a plurality of armsand a crosslinker. The core may be a core a hydrophobic core or ahydrophilic core. For example, a core may be formed by or derived fromcrosslinking of a plurality of homopolymeric arms and a plurality ofcopolymeric arms with a crosslinker, such as a multifunctional monomercrosslinker, for example, a hydrophobic difunctional monomercrosslinker. In certain embodiments, the core may be formed or derivedfrom crosslinking a plurality of hydrophilic polymeric arms and a firstplurality of copolymeric arms, comprising block hydrophilic polymericsegments and block hydrophobic polymeric segments, and a secondplurality of copolymeric arms, comprising block hydrophilic polymericsegments and block salt-tolerant-enhancing polymeric segments, with acrosslinker, such as a hydrophobic difunctional monomer crosslinker, forexample divinylbenzene, wherein the molar ratio of the homopolymericarms to the first copolymeric arms may be between 40:1 to 2:1, and themolar ratio of the homopolymeric arms to the second copolymeric arms maybe between 40:1 to 2:1.

Suitable salt-tolerant star macromolecules may include, but is notlimited to, comprising a core having a molecular weight of greater than3,000 g/mol. For example, a star macromolecule may comprise a corehaving a molecular weight of between 3,000 g/mol and 90,000 g/mol, suchas between 3,000 g/mol and 45,000 g/mol; between 3,000 g/mol and 40,000g/mol; between 3,000 g/mol and 30,000 g/mol; between 3,000 g/mol and20,000 g/mol; between 3,000 g/mol and 15,000 g/mol; between 5,000 g/moland 40,000 g/mol; between 6,000 g/mol and 30,000 g/mol; between 7,000g/mol and 25,000 g/mol; between 8,000 g/mol and 20,000 g/mol; between5,000 g/mol and 15,000 g/mol; between 7,000 g/mol and 12,000 g/mol;between 5,000 g/mol and 9,000 g/mol; between 8,000 g/mol and 10,000g/mol; or between 9,000 g/mol and 15,000 g/mol.

Suitable salt-tolerant star macromolecules may be used to form a clear,homogeneous gel when dissolved in water at a concentration of at least0.05 wt. % at a pH of about 7.5 at STP. For example, a starmacromolecule may form a clear, homogeneous gel when dissolved in waterat a concentration of between 0.05 wt. % to 3 wt. %, such as between 0.1wt. % to 2.5 wt. %; between 0.1 wt. % to 2 wt. %; between 0.2 wt. % to2.0 wt. %; between 0.2 wt. % to 1.5 wt. %; between 0.2 wt. % to 1.0 wt.%; between 0.2 wt. % to 2.5 wt. %; between 0.3 wt. % to 2.5 wt. %;between 0.4 wt. % to 2.0 wt. %; between 0.5 wt. % to 2.0 wt. %; between0.6 wt. % to 2.0 wt. %; between 0.7 wt. % to 1.5 wt. %; between 0.8 wt.% to 1.2 wt. %; between 0.9 wt. % to 1.1 wt. %; between 0.5 wt. % to 2.5wt. %; between 0.75 wt. % to 1.5 wt. %; or between 0.8 wt. % to 1.6 wt.%.

Suitable salt-tolerant star macromolecules, in accordance with the pHEfficiency Range Test Procedure described below herein, may be used toform a clear, homogeneous gel, wherein the star macromolecule at aconcentration of 0.4 wt. %, may have a viscosity of at least 20,000 cP,at a pH of between about 4 to about 12, for example, at a pH of betweenabout 5 to about 11.5 such as at a pH of between about 5 to about 11;between about 5 to about 10.5; between about 5 to about 10; betweenabout 5 to about 9.5; between about 5 to about 9; between about 5 toabout 8.5; between about 5 to about 8; between about 6 to about 11;between about 5.5 to about 10; between about 6 to about 9; between about6.5 to about 8.5; between about 7 to about 8; between about 7.5 to about8.5; or between about 6.5 to about 7.5.

In certain embodiments, for example, suitable salt-tolerant starmacromolecules, in accordance with the pH Efficiency Range TestProcedure described below herein, may be used to form a clear,homogeneous gel, wherein the star macromolecule at a concentration of0.4 wt. %, may have a viscosity of at least 20,000 cP at a pH betweenabout 5.5 to about 11. For example, at a pH between about 5.5 to about11 may have a viscosity of at least 30,000 cP, such as, at least 40,000cP; between 20,000 cP to 250,000 cP; between 20,000 cP to 250,000 cP;between 20,000 cP to 225,000 cP; between 20,000 cP to 200,000 cP;between 20,000 cP to 175,000 cP; between 20,000 cP to 150,000 cP;between 20,000 cP to 125,000 cP; between 30,000 cP to 250,000 cP;between 30,000 cP to 200,000 cP; between 40,000 cP to 175,000 cP; orbetween 40,000 cP to 150,000 cP. For example, a gel at a pH betweenabout 6 to about 11 may have a viscosity of at least 20,000 cP, such as,at least 30,000 cP; at least 40,000 cP; between 20,000 cP to 250,000 cP;between 20,000 cP to 250,000 cP; between 20,000 cP to 225,000 cP;between 20,000 cP to 200,000 cP; between 20,000 cP to 175,000 cP;between 20,000 cP to 150,000 cP; between 20,000 cP to 125,000 cP;between 30,000 cP to 250,000 cP; between 30,000 cP to 200,000 cP;between 40,000 cP to 175,000 cP; or between 40,000 cP to 150,000 cP. Forexample, at a pH between about 7 to about 10.5 may have a viscosity ofat least 60,000 cP, such as at least 70,000 cP; between 60,000 cP to250,000 cP; between 60,000 cP to 225,000 cP; between 60,000 cP to200,000 cP; between 60,000 cP to 175,000 cP; between 60,000 cP to150,000 cP; between 60,000 cP to 125,000 cP; between 60,000 cP to115,000 cP; between 60,000 cP to 105,000 cP; or between 60,000 cP to100,000 cP. For example, at a pH between about 4.5 to about 9.0 may havea viscosity of at least 95,000 cP, such as at least 100,000 cP; between95,000 cP to 250,000 cP; between 95,000 cP to 225,000 cP; between 95,000cP to 200,000 cP; between 95,000 cP to 175,000 cP; between 95,000 cP to150,000 cP; between 95,000 cP to 125,000 cP; between 95,000 cP to115,000 cP; or between 95,000 cP to 105,000 cP.

Suitable salt-tolerant star macromolecules, in accordance with theDynamic Viscosity Test Procedure described below herein, may be used toform a clear, homogeneous gel, wherein the star macromolecule at aconcentration of 0.4 wt. %, may have a viscosity of less than 5,000 cPat a shear rate of 4 sec⁻¹, such as a viscosity of less than 4,000 cP.For example, the star macromolecule at a concentration of 0.4 wt. %, mayhave a viscosity have a viscosity of less than 5,000 cP at a shear rateof 6 sec⁻¹, such as a viscosity of less than 4,000 cP or less than 3,000cP. For example, a gel may have a viscosity of less than 15,000 cP at ashear rate of 0.7 sec⁻¹, such as a viscosity of less than 14,000 cP orless than 13,000 cP. In certain embodiments, suitable gels of thesalt-tolerant star macromolecules of the present invention may have aviscosity of less than 5,000 cP at a shear rate of between 4 and 50sec⁻¹, for example, at a shear rate of between 4 and 45 sec⁻¹; such asbetween 4 and 40 sec⁻¹; between 4 and 30 sec⁻¹; between 4 and 25 sec⁻¹;between 10 and 30 sec⁻¹; between 15 and 25 sec⁻¹; between 20 and 50sec⁻¹; between 30 and 40 sec⁻¹; or between 35 and 50 sec⁻¹. Suitablegels may include, but is not limited to, gels having shear-thinningvalue of at least 5, such as a shear-thinning value of at least 6, orbetween 5 to 15, such as between 5 to 15; between 7 to 12; between 8 to10; or between 6 to 13.

Suitable salt-tolerant star macromolecules, in accordance with theDynamic Viscosity Test Procedure described below herein, include thosethat have a shear-thinning value of at least 6, such as a shear-thinningvalue of between 6 to 100, such as between 15 to 90; between 20 to 80;between 25 to 70; between 25 to 50; or between 30 to 40.

Suitable salt-tolerant star macromolecules, in accordance with theDynamic Viscosity Test Procedure described below herein, include thosethat have a dynamic viscosity value, of greater than 20,000 cP at 1 rpm,and at a concentration of 0.2 wt. %, such as a dynamic viscosity valueof greater than 24,000 cP; greater than 28,000 cP; or greater than30,000 cP at a concentration of 0.2 wt. %.

Suitable emulsions may include, but is not limited to, emulsions thatare emulsifier-free and wherein the emulsion is thickened by suitablesalt-tolerant star macromolecules. For example, the star macromoleculethat may be included in the emulsifier-free emulsion may be awater-soluble star macromolecule, wherein the water-soluble starmacromolecule emulsifies the emulsifier-free emulsion.

Suitable salt-tolerant star macromolecules, include salt-tolerant starmacromolecules that have an emulsion value of greater than 60 minutes,for example, greater than 3 hours, such as greater than 6 hours; greaterthan 10 hours; greater than 20 hours; greater than 40 hours; or greaterthan 100 hours.

Suitable salt-tolerant star macromolecules, according to Formula Z, mayinclude salt-tolerant star macromolecules wherein, for example, P1comprises hydrophilic monomers, P2 comprises salt-tolerant-enhancingmonomers, P3 comprises hydrophilic monomers, P4 comprises hydrophobicmonomers, and P5 comprises hydrophilic monomers. For example, starmacromolecules, according to Formula Z, may include star macromoleculeswherein q2 and q4 may have a value of between 1 to 500, for example,between 1 to 250, such as, between 1 to 150; between 1 to 100; between 1to 75; between 1 to 60; between 1 to 45; between 5 to 40; between 8 to35; between 10 to 30; between 12 to 25; between 14 to 20; between 15 to30; or between 5 to 20; and q1, q3 and/or q5 have a value of between 10to 2000, for example, between 10 to 1500, such as, between 10 to 1000;between 10 to 750; between 10 to 500; between 10 to 400; between 50 to300; between 50 to 200; between 100 to 250; between 125 to 175; between100 to 400; between 150 to 250; between 150 to 350; between 200 to 300;between 150 to 300; between 50 to 150; or between 75 to 125. Forexample, star macromolecules, according to Formula Z, may include starmacromolecules wherein r, s, or t, or the sum of r and t, or the sum ofs and t, may be greater than 5, such as between 5 and 500; between 5 and400; between 5 and 300; between 5 and 200; between 5 and 100; between 5and 90; between 10 and 75; between 15 and 80; between 15 and 70; between15 and 60; between 15 and 50; between 20 and 50; between 25 and 45;between 25 and 35; between 30 and 45; or between 30 and 50. For example,star macromolecules, according to Formula Z, may include starmacromolecules wherein, independently, the molar ratio of r to t, or themolar ratio of s to t, is in the range of between 40:1 to 1:40, such asbetween 40:1 to 1:30; between 40:1 to 1:20; between 40:1 to 1:15;between 40:1 to 1:10; between 40:1 to 1:5; between 40:1 to 2:1; between30:1 to 2:1; between 20:1 to 2:1; between 15:1 to 2:1; between 10:1 to2:1; between 9:1 to 2:1; between 8:1 to 2:1; between 7:1 to 2:1; between6:1 to 2:1; between 5:1 to 2:1; between 4:1 to 2:1; between 3:1 to 2:1;between 2:1 to 1:1; between 8:1 to 3:1; between 7:1 to 2:1; between 7:3to 2:1; between 7:4 to 2:1; between 5:4 to 2:1; or between 5:1 to 3:1.For example, star macromolecules, according to Formula Z, may includestar macromolecules wherein the core may be derived from crosslinkermonomers, such as hydrophobic crosslinker monomers. For example, starmacromolecules, according to Formula Z, may include star macromoleculeswherein the core may comprise crosslinker monomeric residues, such ashydrophobic crosslinker monomeric residues.

Suitable salt-tolerant star macromolecules, may include, but is notlimited to, star macromolecules formed by crosslinking the arms with acrosslinker, such as crosslinking homopolymeric arms and blockcopolymeric arms with a hydrophobic crosslinker. For example, thehomopolymeric arms and the copolymeric arms of a star macromolecule maybe covalently attached to the core via crosslinkage with a crosslinker.For example, a core of a prepared star macromolecule may be prepared bycrosslinking an end of a homopolymeric arm with an end of a copolymericarm, such as an end of a hydrophilic homopolymeric arm with ahydrophilic end of a copolymeric arm. For example, the core of aprepared star macromolecules may be formed by crosslinking anATRP-functional terminal group end of a homopolymeric arm with anATRP-functional terminal group end of a copolymeric arm.

Suitable initiators that may be used to form the salt-tolerant starmacromolecules disclosed herein, may include, but is not limited to,nitroxide initiators, such as stable nitroxide initiators, for example,2,2,6,6-Tetramethylpiperidine-1-oxyl, sometimes called TEMPO; transitionmetal complexes, such cobalt containing complexes; ATRP initiators,comprising halides, such as, bromide, chloride, or iodide, andtransition metal sources, such as, copper, iron, ruthenium transitionmetal sources; iodide with RCTP catalysts, such as germanium or tincatalysts; RAFT initiators, such as dithioesters, dithiocarbamates, orxanthates; ITP catalysts, comprising iodides; tellurium compounds (e.g.,TERP); stibine compounds (e.g., SBRP); or bismuth compounds (e.g.,BIRP). For example, in certain embodiments, an initiator may furthercomprise a monomeric residue, a polymeric segment comprising monomericresidues, or a small-molecule, such as diethyl 2-bromo-2-methylmalonate(DEBMM). For example, in certain embodiments, an initiator may comprisean ATRP initiator, wherein the ATRP initiator serves as a terminalfunctional group. For example, in certain embodiments, an initiator maycomprise an ATRP-functional terminal group, comprising an ATRPinitiator, such as halides and transition metal sources.

Suitable radical initiators that may be used to form the salt-tolerantstar macromolecules disclosed herein, may include, but is not limitedto, azo-containing compounds such as 2,2′-azobis(2-methylpropionitrile(AIBN); a peroxide, for example, benzoyl peroxide (BPO), lauroylperoxide, or cyclohexanone peroxide; a peroxy acid, for example,peroxyacetic acid or peroxybenzoic acid; tert-butyl peracetate;1,1-bis(tert-butylperoxy)-3,3,5-(dibutyl phthalate)trimethylcyclohexane;2,2′-azobis(4-methoxy-2.4-dimethyl valeronitrile) (V-70);2,2′-azobis(2,4-dimethyl valeronitrile) (V-65); dimethyl2,2′-azobis(2-methylpropionate) (V-601);2,2′-azobis(2-methylbutyronitrile) (V-59);1,1′-azobis(cyclohexane-1-carbonitrile) (V-40);2,2′-azobis[N-(2-propenyl)-2-methylpropionamide] (VF-096); orderivatives or combinations thereof. Other suitable radical initiatorsmay include, but are not limited to acetophenone; anisoin;anthraquinone; anthraquinone-2-sulfonic acid sodium salt monohydrate;(benzene) tricarbonylchromium; benzyl; benzoin ethyl ether;4-benzoylbiphenyl;2-benzyl-2-(dimethylamino)-4′-morpholinobutyrophenone;4,4′-bis(diethylamino)benzophenone; camphorquinone;2-chlorothioxanthen-9-one; (cumene)cyclopentadienyliron(II)hexafluorophosphate; dibenzosuberenone; 2,2-diethoxyacetophenone;4,4′-dihydroxybenzophenone; 2,2-dimethoxy-2-phenylacetophenone;4-(dimethylamino)benzophenone; 4,4′-dimethylbenzil;2,5-dimethylbenzophenone; 3,4-dimethylbenzophenone;4′-ethoxyacetophenone; 2-ethylanthraquinone; ferrocene;3′-hydroxyacetophenone; 4′-hydroxyacetophenone; 3-hydroxybenzophenone;4-hydroxybenzophenone; 1-hydroxycyclohexyl phenyl ketone;2-hydroxy-2-methylpropiophenone; 2-methylbenzophenone;3-methylbenzophenone; methybenzoylformate;2-methyl-4′-(methylthio)-2-morpholinopropiophenone; phenanthrenequinone;4′-phenoxyacetophenone; thioxanthen-9-one); or derivatives orcombinations thereof.

Although any conventional method can be used for the synthesis of themulti-arm salt-tolerant star macromolecules of the invention, freeradical polymerization is the preferred and living/controlled radicalpolymerization (CRP) is the most preferred process.

Star polymers are nano-scale materials with a globular shape and can beformed by the “arm first” procedure, can have a crosslinked core and canoptionally possess multiple segmented arms of similar composition. Starscan be designed as homo-arm stars or mikto-arm stars.

Synthesis of star polymers of the invention can be accomplished by“living” polymerization techniques via one of three strategies: 1)core-first” which is accomplished by growing arms from a multifunctionalinitiator; 2) “coupling-onto” involving attaching preformed arms onto amultifunctional core and the 3) arm-first” method which involvescross-linking preformed linear arm precursors using a divinyl compound.

A comparative process is shown in Example 1, which provides a syntheticpathway for preparing the star macromolecule (Advantomer) is amultistep, multi-pot process (Scheme 1). The comparative synthesisrequires extensive purification and drying of the polymer after eachstep which results in the generation of huge amounts of chemical waste(solvents and non-solvents for precipitation) as well as energyconsumption (energy used for drying process). These very longpurification procedures significantly increase the costs of the finalproduction. These purification procedures are required due to lowerconversion of monomer (<65%) which needs to be removed before the nextsynthetic step can be performed. Due to the use of ARGET ATRP, it isimpossible to achieve high monomer conversion and a polymer with highchain-end functionality. The high chain-end functionality is requiredfor the synthesis of the well-defined star macromolecules.

In certain embodiments, the method of making a star macromolecule, suchas a salt-tolerant star macromolecule, comprises a one-pot method. Theadvantages of the “one pot” process for the synthesis of star copolymershas been described and demonstrated in Examples 2-6 (and shown in Scheme2) to generate new well-defined star macromolecules. The one-pot methoddisclosed herein comprises using a novel polymerization technique calledUltimate ATRP instead of ARGET ATRP. This one-pot method uses controlledfeeding of radical initiator to the reaction vessel at very a specifictemperature. This allows reaching high monomer conversion (>70%, suchas >80%) and higher polymer chain-end functionality. This method alsoprovides great control over kinetics and exothermic effects during thepolymerization process. Due to high conversion of the monomer after eachstep, it is possible to continue the polymerization reaction in “onepot” by adding subsequent chemicals without the need for purificationbetween the steps. As a result, the chemical waste is significantlyreduced (just one short washing after step 4 is required) and the fullsynthesis can be performed in much shorter times (3 days vs. 15-20 daysusing the standard comparative process illustrated in Example 1).

In certain embodiments, star macromolecules may be prepared according tothe one-pot method of the present invention, comprising: preparing oneor more of a first arm, and after achieving a high conversion of themonomer, initiate preparing one or more of a second arm in the same pot,while optionally, extending the prepared one or more first arms,followed by crosslinking the prepared one or more first arms and theprepared one or more second arms, washing the resulting product andisolating the final star macromolecule. The one pot method may furthercomprise the preparation of more than two arms in the one pot prior tothe crosslinking step, such as preparing one or more of at least 3 armtypes, at least 4, at least 5, at least 10, at least 15, at least 20 armtypes in the one pot, for example, between 2-30, such as between 2-25,between 2-20, between 2-15, between 2-10, between 2-8, between 2-6,between 3-30, between 3-25, between 3-20, between 3-15, between 3-10,between 3-7, between 3-5, between 4-15, between 5-20, between 5-10,between 10-20, or between 20-30, arm types in the one pot.

In certain embodiments, according to the one pot method of the presentinvention, preparing of one or more of a first arm of a starmacromolecule may comprise feeding a first amount of a radical initiatorin a controlled manner to a reaction vessel containing a first group ofmonomers at a pre-determined temperature, followed by polymerizing thefirst group of monomers to greater than 15% monomer conversion, forexample polymerizing the first group of monomers to greater than 20%monomer conversion, such as greater than 25%; greater than 30%; greaterthan 35%; greater than 40%; greater than 45%; or greater than 50%monomer conversion; for example between 15 and 97% monomer conversion,such as between 15 and 97%; between 15 and 95%; between 15 and 90%;between 15 and 85%; between 15 and 80%; between 15 and 75%; between 15and 70%; between 15 and 65%; between 15 and 50%; between 15 and 45%;between 15 and 40%; between 15 and 35%; between 25 and 97%; between 25and 75%; between 35 and 80%; or between 50 and 97% monomer conversion.Upon achieving greater than 15% monomer conversion in preparing the oneor more first arms, one or more of a second arm of the starmacromolecule, and optionally, extending the prepared one or more firstarms, may begin, comprising: adding a second arm initiator to thereaction vessel, adding a second group of monomers to the reactionvessel, and feeding (at a pre-determined temperature) a second amount ofthe radical initiator in a controlled manner to the reaction vesselcontaining the second arm initiator, the second group of monomers, andoptionally the prepared one or more first arms, followed by polymerizingthe second group of monomers to greater than 15% monomer conversion. Forexample polymerizing the second group of monomers to greater than 20%monomer conversion, such as greater than 25%; greater than 30%; greaterthan 35%; greater than 40%; greater than 45%; or greater than 50%monomer conversion; for example between 15 and 97% monomer conversion,such as between 15 and 97%; between 15 and 95%; between 15 and 90%;between 15 and 85%; between 15 and 80%; between 15 and 75%; between 15and 70%; between 15 and 65%; between 15 and 50%; between 15 and 45%;between 15 and 40%; between 15 and 35%; between 25 and 97%; between 25and 75%; between 35 and 80%; or between 50 and 97% monomer conversion.Upon achieving greater than 15% monomer conversion in preparing the oneor more second arms, and optionally, extending the prepared one or morefirst arms, further arm types may be initiated in the one pot, such as athird arm type, or more than 3 arm types, following similar steps inpreparing the first and second arm types, or the total group of arms maybe crosslinked to form the eventual star macromolecule. If the totalrange of arm types has been achieved, then the monomer conversion isdriven to at least 70% prior to beginning the crosslinking. For exampleafter initiating the preparation of the last arm type to be incorporatedinto the desired star macromolecule, and prior to beginning thecrosslinking step, the polymerization of the monomers in the reactionvessel is driven to greater than 70%, such as greater than 75%; greaterthan 80%; greater than 85%; greater than 90%; greater than 95%; orgreater than 97% monomer conversion, prior to beginning the crosslinkingstep; for example between 70 and 97% monomer conversion, such as between75 and 97%; between 80 and 97%; between 85 and 95%; between 70 and 90%;between 85 and 97%; or between 90 and 97% monomer conversion prior tobeginning the crosslinking step. The crosslinking of the total group ofarms types prepared in the one method, according to the presentinvention, comprises adding the crosslinking agent, and continuing thepolymerization in the one pot. The resulting product may then be washedand isolated.

In certain embodiments, the one pot method of preparing starmacromolecules may reduce the total preparation time of the starmacromolecule by at least 50%, relative to multi-pot preparations, forexample, by at least 55%, such as at least 60%; at least 65%; at least70%; at least 75%; at least 80%; at least 85%; at least 90%; or at least95%, relative to multi-pot preparations. In certain embodiments, the onepot method of preparing star macromolecules may be exclusive ofintermediate purification steps, or may one require one intermediatewashing step or one washing step after crosslinking.

In certain embodiments, the salt-tolerant star macromolecules of thepresent invention, and those made by the methods of preparing the same,may be used as a salt-tolerant thickening agent, such as a salt-tolerantthickening agent in aqueous media, or an oil-based media, or a mixedwater and oil-based media. In certain embodiments, a method of making orpreparing a salt-tolerant composition may include adding a salt-tolerantstar macromolecule disclosed herein, such that when dissolved in waterat a concentration of at least 0.3 wt. % forms a homogeneous gel and hasa dynamic viscosity of at least 10,000 cP in a 0.4 wt. % NaCl aqueoussolution, according to the Salt Tolerance Test. In certain embodiments,a method of making an aqueous composition salt-tolerant may includeadding at least 0.3 wt. % of a salt-tolerant star macromoleculedisclosed herein to an aqueous composition, wherein the salt-tolerantstar macromolecule when dissolved in water at a concentration of atleast 0.3 wt. % forms a homogeneous gel and has a dynamic viscosity ofat least 10,000 cP in a 0.4 wt. % NaCl aqueous solution, according tothe Salt Tolerance Test.

Without wishing to be bound to a particular mechanism, the observedsalt-tolerance of the salt-tolerant star macromolecules, andcompositions using the same, in aqueous mixtures is alterable based onthe type of salt-tolerant-enhancing monomers included in the stars, forexample, ionizable monomers, anionic monomers, cationic monomers, orhydrogen-bonding capable monomers, such as hydrogen bond donatingmonomers or hydrogen bond accepting monomers. In certain embodiments,the salt-tolerant star macromolecules comprise at least two types ofarms: a first arm type comprising hydrophilic polyelectrolytes arms, anda second arm type comprising a hydrophilic polyelectrolytes block and asalt-tolerant-enhancing block. In certain embodiments, the salt-tolerantstar macromolecules comprise at least three types of arms: a first armtype comprising hydrophilic polyelectrolytes arms, a second arm typecomprising a hydrophilic polyelectrolytes block and asalt-tolerant-enhancing block, and a third arm type comprising ahydrophilic polyelectrolytes block and a hydrophobic block. These armsare covalently attached to the core of the star at the ends ofhydrophilic blocks.

When the salt-tolerant star macromolecule is an amphiphilic starpolymer, partially or totally neutralized by base in water solution, thenegative charges repellent on hydrophilic chains may help stretching ofthe hydrophilic arms in water which may be good for increasing theviscosity of the solution. Meanwhile, the hydrophobic blocks mayassociate together due to the hydrophobic interactions in watersolution. In this way, different star polymer molecules may be connectedto form a large net in water solution and increase the viscosity ofwater. As salts are added to the polymer solution, the shrink ofhydrophilic chains can break the hydrophobic interactions betweenhydrophobic chains. The dissociation of the polymer network and shrinkof hydrophilic arms may result in the loss of viscosity.

The hydrophobic copolymeric chains having hydrogen bond donors oracceptors functional groups can form hydrogen bonds with water so thehydrophobic chains can have better stretch in water than thosehydrophobic polymer chains without hydrogen bonds with water. The betterstretch of these hydrophobes may contribute larger interface tohydrophobic interactions as they associate together. While salts areadded, the hydrogen bonds between hydrophobic chains and water arebroken from partially to totally with the increase amount of salts. As aresult, the circumstance around the hydrophobic polymer chains may turnto more hydrophobic and may lead to stronger hydrophobic interactionsbetween hydrophobic chains, which may strengthen the polymer network. Asfor the hydrophilic chains, the addition of salts may weaken thenegative charges repellent along the chains and the arms may tend toshrink. Such tendency increases as the amount of electrolytes increases.In the presence of salts, the enhanced hydrophobic interactions betweenhydrophobes tend to reinforce the polymer network while the weakenednegative charge repulsions tend to pull the network apart. With theaddition of salts, if the increase of the hydrophobic interactionsbetween hydrophobes can counteract or surpass the increase of shrinkingof hydrophilic chains, the viscosity may retain or even increase. But asthe growing force of shrink is stronger than the hydrophobicinteractions between hydrophobes, the connections between stars maygradually break and consequently the viscosity will decrease gradually.This may be a major reason for salt-tolerant effect. When hydrogen bonddonor or acceptors moieties are introduced into hydrophobes of the starpolymers disclosed herein, the observed viscosity increased and thengradually decreased as the amount of salt increased. In star polymershaving hydrophobic chains without hydrogen bond donors or acceptorsmoieties, a sharp decrease in viscosity was observed when salts areadded.

While all above controlled polymerization procedures are suitable forpreparation of an embodiment of the disclosed self assembling starmacromolecules, other embodiments are also exemplified, for example, thepreparation of the self assembling multi-arm stars with narrow MWD, incontrast to prior art using ATRP. The reason for the use of theControlled Radical Polymerization process (CRP) known as ATRP; disclosedin U.S. Pat. Nos. 5,763,546; 5,807,937; 5,789,487; 5,945,491; 6,111,022;6,121,371; 6,124,411: 6,162,882: and U.S. patent application Ser. Nos.09/034,187; 09/018,554; 09/359,359; 09/359,591; 09/369,157; 09/126,768and 09/534,827, and discussed in numerous publications listed elsewherewith Matyjaszewski as co-author, which are hereby each incorporated intothis application in their entirety, is that convenient procedures weredescribed for the preparation of polymers displaying control over thepolymer molecular weight, molecular weight distribution, composition,architecture, functionality and the preparation of molecular compositesand tethered polymeric structures comprising radically (co)polymerizablemonomers, and the preparation of controllable macromolecular structuresunder mild reaction conditions.

An aspect of the present invention relates to the preparation and use ofmulti-arm star macromolecules by an “arm first” approach, discussed byGao, H.; Matyjaszewski, K. JACS; 2007, 129, 11828. The paper and citedreferences therein are hereby incorporated by reference to describe thefundamentals of the synthetic procedure. The supplemental informationavailable within the cited reference provides a procedure forcalculation of the number of arms in the formed star macromolecule.

It is expected that biphasic systems such as a mini-emulsion or an abinitio emulsion system would also be suitable for this procedure sincemini-emulsion systems have been shown to function as dispersed bulkreactors [Min, K.; Gao, H.; Matyjaszewski, K. Journal of the AmericanChemical Society 2005, 127, 3825-3830] with the added advantage ofminimizing core-core coupling reactions based on compartmentalizationconsiderations.

In one embodiment star macromolecules are prepared with composition andmolecular weight of each segment predetermined to perform as rheologymodifiers in aqueous based solutions. The first formed segmented linearpolymer chains are chain extended with a crosslinker forming acrosslinked core.

In another embodiment, a simple industrially scalable process for thepreparation of star macromolecules is provided wherein the arms comprisesegments selected to induce self assembly and wherein the selfassemblable star macromolecules are suitable for use as rheology controlagents in waterborne and solvent-borne coatings, adhesives, andfracturing fluid compositions.

An embodiment of the present invention can be exemplified by thepreparation of a multi-arm star macromolecule wherein the number of armsin the star macromolecule is between 5 and 500, preferentially between10 and 250, with segments selected to induce self assembly when the starmacromolecule is dispersed in a liquid wherein the self assemblable starmacromolecules are suitable for use as thickening agents or rheologymodifiers in cosmetic and personal care compositions at lowconcentrations of the solid in the thickened solution, preferably lessthan 5 wt. %, and optimally less than 1 wt. %. The dispersion medium cancomprise aqueous based systems or oil based systems.

Similar structures can also be prepared using the macromonomer method ora combination of the macromonomer and macroinitiator method in acontrolled polymerization process, or even through free radicalcopolymerization conducted on macromonomers, as known to those skilledin the art. [Gao, H.; Matyjaszewski, K. Chem.-Eur. J. 2009, 15,6107-6111.]

Both the macromonomer and macroinitiator procedures allow incorporationof polymer segments prepared by procedures other than CRP [WO 98/01480]into the final star macromolecule. Polymer segments can comprisesegments that are bio-degradable of are formed from monomers preparedfrom biological sources.

As noted above the first formed ATRP macroinitiator can be prepared byconducting a sequential ATRP (co)polymerization ofsalt-tolerant-enhancing, hydrophobic, and/or hydrophilic monomers orprecursors thereof or can be prepared by other polymerization proceduresthat provide a functional terminal atom or group that can be convertedinto an ATRP initiator with a bifunctional molecule wherein onefunctionality comprises a transferable atom or group and the otherfunctionality an atom or group that can react with the functionalityfirst present on the (co)polymer prepared by a non-ATRP procedure. [WO98/01480]

In aqueous solutions, the composition and molecular weight of the outershell of hydrophobes, or agents that participate in molecularrecognition, can be selected to induce self-assembly into aggregates andact as physical crosslinkers. Above a certain concentration,corresponding to the formation of a reversible three dimensionalnetwork, the solutions will behave as physical gels thereby modifyingthe rheology of the solution.

In one embodiment, the polymer compositions of the invention havesignificantly lower critical concentration for network (gel) formationcompared to networks formed with block copolymers, graft and stars witha low specific number of attached arms due to:

-   -   multi-arm structure (many transient junctions possible between        hydrophobic parts of the stars)    -   very high molecular weight of each star (5 thousand to 5 million        or higher) allows high swelling ratio of the molecules in        solution    -   molecular organization on larger scales (>1 μm)

Whereas the examples above and below describe the preparation and use ofblock copolymers as arms with a well defined transition from one segmentto the adjoining segment a segmented copolymer with a gradient incomposition can also be utilized. The presence of a gradient can becreated by addition of a second monomer prior to consumption of thefirst monomer and will affect the volume fraction of monomer unitspresent in the transition form one domain to another. This would affectthe shear responsiveness of the formed star macromolecule.

Star macromolecules with narrow polydispersity comprising arms withblock copolymer segments can be formed with as few as 5 arms byselecting appropriate concentration of reagents, crosslinker andreaction temperature.

Star macromolecules can be prepared in a mini-emulsion or reversemini-emulsion polymerization system. The first formed block copolymersare used as reactive surfactants for star synthesis by reaction with aselected crosslinker in mini-emulsion.

In an embodiment, the polymer compositions having salt-tolerant starmacromolecules of the present invention, the salt-tolerant starmacromolecule, emulsifier, gel, emulsifier-free emulsion, emulsionand/or thickening agent, including those formed by a one-pot process,ATRP, CRP, and/or combinations of one or more of these processes, may beused to provide a certain level of control over viscosity andconsistency factors in many aqueous and oil based systems including, forexample, fracking fluid additives, gelling agents, gels, proppantstabilizers, breakers, friction reducers, thickening agents.

In an embodiment, the salt-tolerant star macromolecules of the presentinvention (or the polymer compositions having the same), may be suitablein oil and gas applications, including but not limited to, as rheologymodifiers for fracturing fluids/drilling well fluids, gelling agents,gels, dispersants, proppant stabilizers and carriers, breakers, frictionreducers, lubricants, scale-buildup inhibitors, heat transfer fluids,thickening agents, additives to improve oil extraction from oil sands,emulsion breakers for oil-sand-water emulsions, or additives to improvedewatering of oil sands.

In an embodiment, the salt-tolerant star macromolecules of the presentinvention (or the polymer compositions having the same), may be suitablein mining applications, including but not limited to, dust suppressants,flocculating agents, gold and precious metal extraction, and preciousmetal processing, lubricants and drag reduction agents for pipelineslurry transport.

In an embodiment, the salt-tolerant star macromolecules of the presentinvention (or the polymer compositions having the same), may be suitablein cosmetic and personal care applications, including but not limitedto, cosmetic creams, lotions, gels, sprayable lotion, sprayable cream,sprayable gel, hair styling sprays and mousses, hair conditioners,shampoos, bath preparations, ointments, deodorants, mascara, blush, lipstick, perfumes, powders, serums, skin cleansers, skin conditioners,skin emollients, skin moisturizers, skin wipes, sunscreens, shavingpreparations, solids, and fabric softeners.

In an embodiment, the salt-tolerant star macromolecules of the presentinvention (or the polymer compositions having the same), may be suitablein home care applications, including but not limited to, cleaners forwindows and glass, and other household surfaces, toilet areas, enzymeproduction, drain cleaners, liquid and gelled soaps, polishes and waxes,liquid and powdered detergents including detergents for laundry and indish washing.

In an embodiment, the salt-tolerant star macromolecules of the presentinvention (or the polymer compositions having the same), may be suitablein adhesive applications, including but not limited to, associativecomplexes, billboard adhesives, carpet backsizing compounds, hot meltadhesives, labeling adhesives, latex adhesives, leather processingadhesives, plywood laminating adhesives, paper adhesives, wallpaperpastes, wood glue.

In an embodiment, the salt-tolerant star macromolecules of the presentinvention (or the polymer compositions having the same), may be suitablein electronic applications, including but not limited to, antistaticfilm and packaging, conductive inks, rheology control agents used forcopper foil production, multilayer ceramic chip capacitors,photoresists, plasma display screens, lubricants for wire, cable, andoptical fibers, gel lacquers for coil coating.

In an embodiment, the salt-tolerant star macromolecules of the presentinvention (or the polymer compositions having the same), may be suitablein medical and pharmaceutical applications, including but not limitedto, but not limited to, medical device lubrication, antibacterialcoatings, pharmaceutical excipients such as binders, diluents, fillers,lubricants, glidants, disintegrants, polish agents, suspending agents,dispersing agents, plasticizers.

In an embodiment, the salt-tolerant star macromolecules of the presentinvention (or the polymer compositions having the same), may be suitablein paper applications, including but not limited to, coatings,dispersion for tissue and thin papers, filler retention and drainageenhancement, flocculation and pitch control, grease-proof coatings,adhesives, release coatings, surface sizing, sizes for gloss and inkholdout, tail tie and pickup adhesives for papermaking.

In an embodiment, the salt-tolerant star macromolecules of the presentinvention (or the polymer compositions having the same), may be suitablein agricultural applications, including but not limited to, animal feed,dispersing agents, drift control, encapsulation, seed coatings, seedtape, spray adherents, water-based sprays and spray emulsions,water-soluble packaging.

In an embodiment, the salt-tolerant star macromolecules of the presentinvention (or the polymer compositions having the same), may be suitablein other applications including but not limited to, water- andsolvent-based coating compositions, water- and solvent-based lubricants,water- and solvent-based viscosity index modifiers, paints,plasticizers, antifoaming agents, antifreeze substances, corrosioninhibitors, detergents, dental impression materials, dental fillers,inkjet printer ink and other inks, ceramic and brick forming,prepolymers such as polyols for use in polyesters, polyurethanes,polycarbonates. For rheology modifier applications, characteristics arehigh gel strength, stability in the presence of salt and increasedtemperatures, high shear thinning characteristics, forms versatile lowviscosity soluble concentrations, and synergistic interactions withadded agents to adjust their rheology profile to optimize propertiessuch as sedimentation, flow and leveling, sagging, spattering, etc.

EXAMPLES

TABLE 1 Commercial Abbreviation Name Form Purity Source St styreneliquid 99% Sigma Aldrich MMA methyl methacrylate liquid 99% SigmaAldrich tBA tert-butyl acrylate liquid 98% Sigma Aldrich tBMA tert-butylmethacrylate liquid 98% Sigma Aldrich AA acrylic acid (formed bydeprotection) NA NA NA MAA methacrylic acid (formed by deprotection) NANA NA Me6TREN tris[2-(dimethylamino)ethyl]amine liquid 95% ATRPSolutions TPMA tris(2-pyridylmethyl)amine solid 95% ATRP Solutions bpy2,2′-bipyridine solid 99% Sigma Aldrich AIBN2,2′-Azobis(2-methylpropionitrile) solid 98% Sigma Aldrich Sn(EH)2tin(II) 2-ethylhexanoate liquid 95% Sigma Aldrich DVB divinylbenzeneliquid 80% Sigma Aldrich FA formic acid liquid 99% Sigma Aldrich THFtetrahydrofuran liquid 99.9%  Sigma Aldrich NaOH sodium hydroxide solid98% Sigma Aldrich EBiB ethyl α-bromoisobutyrate liquid 98% Sigma AldrichDEBMM diethyl 2-bromo-2-methylmalonate liquid 98% Sigma Aldrich DMFdiethylformamide liquid 98% Sigma Aldrich anisole liquid 99% SigmaAldrich acetonitrile liquid 99.8%  Sigma Aldrich NaCl sodium chloridesolid 99.7%  Fisher Chemical V-70 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile) solid Wako HC1 hydrochloric acid liquid 37% Sigma AldrichACHX 1,1′-azobis(cyclohexane-1-carbonitrile) solid 98% Sigma Aldrich HEAhydroxyethyl acrylate TFA trifluroacetic acid Methylene chloride liquid99.6% DMAEMA 2-(dimethylamino)ethyl methacrylate PEGMA (polyethyleneglycol) methacrylate NIPAM N-isopropylacrylamide

Synthesis of Star Copolymers (Examples 1-6) Example 1 Preparation of a(St₁₅-b-AA₂₉₀/AA₁₅₀) Miktoarm Star Macromolecule (Referenced Herein asAdvantomer)

A four step procedure was developed for the preparation of apoly(acrylic acid) based miktoarm star macromolecule and is described inScheme 1. 0.55 kg of the miktoarm star macromolecule with St₁₅-b-AA₂₉₀and AA₁₅₀ arms (molar ratio of arms: 1/4) was prepared as follows.

STEP 1: Synthesis of a Polystyrene Macroinitiator (St₁₅) Having 15 DP

A polystyrene macroinitiator was formed using ICAR ATRP by introducingthe following components into the 4-L reaction vessel: 2500 mL of St,83.7 mL of DEBMM, 195 mg of CuBr₂, 253 mg of TPMA, 3.6 g of AIBN, 10 mLof DMF, and 75 mL of anisole (corresponds to molar ratio:St/DEBMM/CuBr₂/TPMA/AIBN=50/1/0.002/0.003/0.05) at T=60° C., t=10.2 h.The reaction was run to ˜30% conversion. The resulting reaction productwas purified to obtain the PSt in powder form (yield˜650 g). A portionof the St₁₅ powder was dissolved in THF and passed through the GPCcolumn. The measured molecular weight of the hydrophobic, polystyrenesegment=1600 which is equivalent to an average degree of polymerization(DP) of about 15-16 and the PDI was measured to be 1.24.

STEP 2: Synthesis of Polystyrene-b-Poly(t-Butyl Acrylate) andPoly(t-Butyl Acrylate) Macroinitiator

The following components were introduced into the 4-L reaction vessel inthe following molar ratio: tBA/St₁₅ (from Example 1, Step1)/CuBr₂/TPMA/Sn(EH)₂=200/0.2/0.01/0.06/0.1, in anisole at T=55° C.(corresponds to amounts: 2400 mL of tBA, 26.9 g of PSt from Example 1 inStep 1, 188 mg of CuBr₂, 1.46 g TPMA, 2.7 mL of Sn(EH)₂, 100 mL of DMF,and 1100 mL of anisole). About 2.0 hours after the reaction wasinitiated, the conversion of the tBA reached about 6% and a portion ofthe St₁₅-b-tBA was recovered and measured by GPC with the followingresults M_(n)=19,800 g/mol; PDI=1.16. It was determined that thefollowing St₁₅-b-tBA₁₄₀ copolymeric block was obtained. Then, 0.8 molarratio amount (9.87 mL), relative to the initially introduced components,of EBiB was injected into the polymerization mixture. The reaction wascontinued and stopped after about 19.8 h when the conversion of themonomer reached 61%. The reaction product was purified by precipitationinto 40 L of methanol/water (10/1 v/v) and next dried in the vacuum ovenfor 48 h at 50° C. (yield: 1250 g of polymer product). Next, polymer wasanalyzed by GPC. Based on the GPC measured the final molecular weight ofthe product was determined to be poly(t-butyl acrylate) segment in theblock copolymer was ˜37,200 g/mol, St₁₅-b-tBA₂₉₀, and the molecularweight of poly(t-butyl acrylate) initiated from EBiB was 19,200 g/molwhich is equivalent to a DP=150, tBA₁₅₀. The overall molecular weight ofmixture of arms resulted in M_(n)=20,800 g/mol and PDI=1.27.

STEP 3: Synthesis of the (St₁₅-b-tBA₂₉₀/tBA₁₅₀) Miktoarm StarMacromolecule

A mikto multi-arm star macromolecule was prepared by conducting afurther chain extension reaction with the polymer St₁₅-b-tBA₂₉₀/tBA₁₅₀formed in Example 1, Step 2. The reaction was conducted with a moleratio of macroinitiators to divinylbenzene of 1:16 in anisole. Thefollowing components were introduced into the 4-L reaction vessel: 115mL of DVB, 1050 g of St₁₅-b-tBA₂₉₀/tBA₁₅₀ from Example 1 in Step 2, 225mg of CuBr₂, 1.03 g of TPMA, 2.45 mL of Sn(EH)₂, 115 mL of DMF, and 2500mL of anisole (corresponds to molar ratio:DVB/[St₁₅-b-tBA₂₉₀/tBA₁₅₀](from Example 1, Step2)/CuBr₂/TPMA/Sn(EH)₂=16/1/0.02/0.07/0.15), T=95° C., t=20.6 h. Thereaction product was purified via precipitation into 40 L of methanoland next dried in the vacuum oven for 48 h at 50° C. (yield: 1050 g ofpolymer product). Next polymer was analyzed by GPC. The GPC apparentmolecular weight of the star was 109,400 with a PDI 1.52, which wouldindicate an average of six arms but this is an underestimate of theactual number of arms since the star molecule is a compact molecule.Indeed in this situation, the number of arms in the star molecule isclose to 30.

STEP 4: Deprotection of the (St₁₅-b-tBA₂₉₀/tBA₁₅₀) to(St₁₅-b-AA₂₉₀/AA₁₅₀) Star

Deprotection of the (St₁₅-b-tBA₂₉₀/tBA₁₅₀) star macromolecule to(St₁₅-b-AA₂₉₀/AA₁₅₀) star block copolymer to provide water solublepoly(acrylic acid) segments in the mikto multi-arm star macromolecule.The St₁₅-b-tBA₂₉₀/tBA₁₅₀ arms of the miktoarm star macromolecule weretransformed to St₁₅-b-AA₂₉₀/AA₁₅₀ arms with the following procedure. 900g of polymer (St₁₅-b-tBA₂₉₀/tBA₁₅₀) (from Experiment 1, Step 3) wasdissolved in 7200 mL of methylene chloride and 245 mL of trifluoroaceticacid to deprotect tBu groups, the reaction was performed at roomtemperature for 60.0 h. Then polymer was decanted and washed 3 timeswith 2 L of acetonitrile. Polymer was then solubilized in 5 L of THF andprecipitated into 50 L of acetonitrile. The star macromolecule was driedin vacuum oven for 3 days at 50° C. The amount of polymer obtained afterpurification was 550 g, which would correspond to full conversion of tBAto AA.

Example 2 Preparation of a ((St₁₉-Co-MAA₄)-b-AA₃₂₅/AA₉₈) StarMacromolecule

The simple “one-pot” procedure was developed for the preparation of apoly(acrylic acid) based miktoarm star macromolecule and is described inScheme 2. The miktoarm star macromolecule with (St₁₉-co-MAA₄)-b-AA₃₂₅and AA₉₈ arms (molar ratio of arms: 1/4) was prepared as follows.

STEP 1: Synthesis of a Poly(Styrene-Co-Tert-Butyl Methacrylate)Macroinitiator (St₁₉-Co-tBMA₄) Having 23 DP

A copolymer poly(styrene-co-tert-butyl methacrylate) macroinitiator wasformed using ICAR ATRP by introducing the following components into the100 mL reaction vessel at the following molar ratio:St/tBMA/EBiB/CuBr₂/Me6TREN/ACHX=40/10/1/0.003/0.06/0.03 (corresponds toamounts: 40 mL of St, 13.8 of tBMA, 1.28 mL of EBiB, 5.8 mg of CuBr₂,0.14 mL of Me6TREN, 64 mg of ACHX, 2 mL of anisole, and 0.5 mL of DMF)at T=90° C., t=5.4 h. The reaction was run to ˜25% conversion. Theresulting reaction product was purified to obtain the St₁₉-co-tBMA₄copolymer in a powder form (yield: 9 g). A portion of the St₁₉-co-tBMA₄powder was dissolved in THF and passed through the GPC column. The GPCtrace obtained for the macroinitiator is shown in FIG. 1. The measuredmolecular weight of the hydrophobic, poly(styrene-co-tert-butylmethacrylate) segment=2,500 g/mol which is equivalent to an averagedegree of polymerization (DP) of about 19 and 4 for styrene andtert-butyl methacrylate respectively, and the PDI was measured to be1.69.

STEP 2: One-Pot Synthesis of Poly(Styrene-Co-Tert-ButylMethacrylate)-b-Poly(Tert-Butyl Acrylate) and Poly(Tert-Butyl Acrylate)Arms

The following components were introduced into the 1-L reaction vessel:300 mL of tBA, 6.6 g of St₁₉-co-tBMA₄ from Example 2 in Step 1, 29.3 mgof CuBr₂, 0.17 mL Me6TREN and 150 mL of anisole (corresponding molarratio: tBA/P(St₁₉-co-tBMA₄) (from Example 2, Step1)/CuBr₂/Me6TREN=160/0.2/0.01/0.05), at T=65° C. Polymerization wasstarted by continuous feeding solution of V-70 (101 mg) in acetone (30mL) to the reaction mixture with the rate of 4.5 mL/h. This rate wasadjusted during the polymerization process in order to control thekinetics and exothermic effects of the reaction. About 3.0 hours afterthe reaction was initiated, the conversion of the tBA reached about 21%and a portion of the (St₁₉-co-tBMA₄)-b-tBA was recovered and measured byGPC with the following results: M_(n)=31,700 g/mol, PDI=1.61. It wasdetermined that the following (St₁₉-co-tBMA₄)-b-tBA₂₂₈ copolymeric blockwas obtained. The feeding of V-70 was stopped and then, 1.54 mL of EBiB(0.8 molar ratio amount relative to the initially introduced components)was injected into the polymerization mixture. The reaction was continuedby feeding V-70 and stopped after about 6.9 h by stopping feeding V-70,stopping heating and opening reactor to air. Based on the GPC measuredvalues the final molecular weight of poly(tert-butyl acrylate) segmentin the block copolymer (St₁₉-co-tBMA₄)-b-tBA₃₂₅ was ˜44,300 g/mol andthe molecular weight of poly(tert-butyl acrylate) initiated from EBiBwas 12,600 g/mol which is equivalent to a DP=98. The overall molecularweight of mixture of arms resulted in M_(n)=20,100 g/mol and PDI=1.97.The GPC curves of the macroinitiator St₁₉-co-tBMA₄ and the mixture offormed block copolymer arms (St₁₉-co-tBMA₄)-b-tBA₃₂₅ and poly(tert-butylacrylate) arms tBA₉₈ are shown in FIG. 2. The signal from blockcopolymer is overlapping with signal from homopolymer arms but thisresult clearly indicates that a clean chain extension from St₁₉-co-tBMA₄macroinitiator had occurred.

STEP 3: One-Pot Synthesis of the ((St₁₉-Co-tBMA₄)-b-tBA₃₂₅/tBA₉₈) StarMacromolecule

A mikto multi-arm star macromolecule was prepared by continuing areaction in Step 2 in Example 2 and performing a crosslinking of theblock copolymer and homopolymer arms. The synthesis started with thepolymer solutions obtained above (Example 2, Step 2). To this 1-Lreactor vessel were added following components: 450 mL of anisole, 24 mgof CuBr₂, 198 mg of TPMA, 15 mL of DMF, 35 mL of DVB and 0.5 mL ofSn(EH)₂ (corresponds to molar ratio:DVB/[(St₁₉-co-tBMA₄)-b-tBA₃₂₅/tBA₉₈](from Example 2, Step2)/CuBr₂/TPMA/Sn(EH)₂=18/1/0.008/0.05/0.1), T=95° C., t=19.5 h. The GPCcurves and results of the star forming reaction are provided in FIG. 3.It can be seen that a multi-arm star macromolecule with a crosslinkedcore was formed. The GPC apparent molecular weight of the star was51,200 with a PDI 1.78, which would indicate an average of three armsbut this is an underestimate of the actual number of arms since the starmolecule is a compact molecule. Indeed in this situation, the number ofarms in the star molecule is close to 30. The number of arms can bemodified by conducting the core forming reaction with a different ratioof crosslinking agent to arm precursor or by running the reaction with adifferent concentration of reagents.

STEP 4: Deprotection of the ((St₁₉-Co-tBMA₄)-b-tBA₃₂₅/tBA₉₈) to((St¹⁹⁻co-MAA₄)-b-AA₃₂₅/AA₉₈) Star

Deprotection of the ((St₁₉-co-tBMA₄)-b-tBA₃₂₅/tBA₉₈) star macromoleculeto ((St₁₉-co-MAA₄)-b-AA₃₂₅/AA₉₈) star block copolymer to provide watersoluble poly(acrylic acid) segments in the mikto multi-arm starmacromolecule. The (St₁₉-co-tBMA₄)-b-tBA₃₂₅/tBA₉₈ arms of the miktoarmstar macromolecule were transformed to ((St₁₉-co-MAA₄)-b-AA₃₂₅/AA₉₈ armswith the following procedure. The 120 mL of the polymer solution fromthe Example 2, Step 3 was transferred to the 250 mL reaction vessel. Tothis vessel 33.6 mL of formic acid and 3 mL of concentrated HCl wereadded to deprotect tBu groups. The reaction was performed at 75° C. for18.0 h. Then solid polymer (formed during the reaction) was decanted andwashed 3 times with acetonitrile. Polymer was dried in the vacuum ovenat 50° C. for 24 h and next solubilized in THF and precipitated intoacetone/acetonitrile mixture. The star macromolecule was dried in vacuumoven for 2 days at 50° C. (yield 20 g). Based on the gravimetricalanalysis full conversion of tBA and tBMA to AA and MAA respectively wasachieved.

Example 3 Synthesis of (MMA₁₅-b-AA₃₆₇/AA₈₂) Star

The simple “one-pot” procedure was developed for the preparation of apoly(acrylic acid) based miktoarm star macromolecule similar to thatdescribed in Scheme 2. The miktoarm star macromolecule withMMA₁₅-b-AA₃₆₇ and AA₈₂ arms (molar ratio of arms: 1/4) was prepared asfollows.

STEP 1: Synthesis of a Poly(Methyl Methacrylate) Macroinitiator (MMA₁₅)Having 15 DP (#08-007-33)

MMA₁₅ macroinitiator was synthesized by using Atom Transfer RadicalPolymerization (ATRP). The molar ratio of reagents is:MMA/DEBMM/CuBr/CuBr₂/bpy=22/1/0.2/0.02/0.44 in DMF (50% v/v). 150 mL ofMMA, 12 mL of DEBMM, 0.31 g of CuBr₂, 4.37 g of bpy and 150 mL of DMFwere added to a 500 mL round bottom flask. The flask was sealed with arubber septum and the solution was purged with nitrogen for 1 hour.Under the nitrogen flow, the flask was opened and 1.8 g of CuBr wasquickly added. Then the flask was sealed and heated up to 50° C. 2.5hours later, the reaction was stopped. The polymer was precipitated tomethanol and the molecular weight was measured by GPC. The Mn is 1525g/mol and PDI is 1.06. Yield: 80 grams of polymer was obtained afterpurification.

STEPS 2-4: Synthesis of MMA₁₅-b-tBA₃₆₇/tBA₈₂ Arms, Crosslinking andDeprotection to Produce (MMA₁₅-b-AA₃₆₇/AA₈₂) Star Copolymer in “One Pot”(#12-027-12)

The synthesis includes 3 steps: the synthesis of arms, the cross-linkingof arms and the deprotection of star polymers. For the synthesis ofarms, the molar ratio of reagents is: tBA/MMA₁₅ (from Example 3, Step1)/EBiB/CuBr₂/Me₆TREN/V-70=160/0.2/0.8/0.01/0.05/0.025. Anisole was usedas solvent (39% v/v). The synthesis of arms was conducted as follows. 18g of MMA₁₅, 1400 mL of tBA and 900 mL of anisole were add to a 4 L AceGlass reactor. In a 100 mL beaker 133.6 mg CuBr₂ was dissolved in 48 mLDMF with 0.8 mL Me₆TREN. Then CuBr₂/Me₆TREN in DMF was added to the 4 Lreactor. The polymer solution was stirred for 10 min in order todissolve MMA₁₅ macroinitiator. The 4 L Ace Glass reactor was closed andthe polymer solution was purged with nitrogen for 1.0 h. In a 50 mLflask, 460.4 mg of V-70 was dissolved in 30 mL of acetone and purgedwith N₂. The solution of V-70 in acetone was then transferred into 60 mLsyringe under N₂. The 4 L Ace Glass reactor was heated up to 65° C. andV-70 in acetone was fed at the rate of 5 mL/h. This rate was adjustedduring the polymerization process in order to control the kinetics andexothermic effects of the reaction. Sample was taken for analysis and asthe monomer conversion reached 36%, 7.0 mL of EBiB was injected. ThenV-70 was fed at 5 mL/h rate. 2 hours later, the monomer conversionreached 87%, and the synthesis of arms was finished. The cross-linkingof arms was continued in the same reactor with the molar ratio as:[MMA₁₅-b-tBA₃₆₇/tBA₈₂]/DVB/CuBr₂/TPMA/Sn(EH₂)=1/25/0.02/0.2/0.2. 70 mLof CuBr₂/TPMA in DMF solution, 130 mL of DVB and 1600 mL of anisole wereadded to the reactor and purged with N₂ for 1 hour. Then the polymersolution was heated up to 95° C. After 19 hours, the conversion of DVBreached 68%, the heating was stopped and the reactor was opened to air.The molecular weight of (MMA₁₅-b-tBA₃₆₇/tBA₈₂) star molecule wasdetermined by GPC. Mn=50649 g/mol, PDI=2.27. The deprotection wasconducted by adding 700 mL of formic acid and 0.8 mL sulfuric acid tothe reactor. The solutions was heated up to 75° C. and stirred for 15hours. Then the liquid was decanted and the solid polymer was washedwith acetonitrile and acetone for 3 times in the reactor. The solidpolymer was recovered and dried in vacuum oven at 40° C. for 1 day.Yield: the mass of (MMA₁₅-b-AA₃₆₇/AA₈₂) star was 590 grams.

Example 4 Synthesis of (MMA₂₂-b-AA₇₆₂/AA₅₉) Star

The simple “one-pot” procedure was used for the preparation of apoly(acrylic acid) based miktoarm star macromolecule similar to thatdescribed in Scheme 2. The miktoarm star macromolecule withMMA₂₂-b-AA₇₆₂ and AA₅₉ arms (molar ratio of arms: 1/4) was prepared asfollows.

STEP 1: Synthesis of a Poly(Methyl Methacrylate) Macroinitiator (MMA₂₂)Having 22 DP (#12-027-56)

MMA₂₂ macroinitiator was synthesized by using Activators ReGenerated byElectron Transfer (ARGET) ATRP. The molar ratio of reagents is:MMA/DEBMM/CuBr₂/TPMA/Sn(EH₂)=50/1/0.005/0.0175/0.05 in anisole (20%v/v). In a 250 mL round bottom flask, 60 mL of MMA and 2.14 mL of DEBMMwere added to 12 mL of anisole. 1.5 mL of pre-mixed CuBr₂/TPMA in DMFsolution was added to the flask. The flask was sealed with a rubberseptum and the solution was purged with nitrogen for 1.0 hour. The flaskwas then placed in an oil bath set at 75° C. 0.193 mL of Sn(EH₂) wasinjected and the reaction started. Samples were taken to monitor themonomer conversion. After 23 hours, the flask was opened to air and thereaction was stopped. The polymer was purified by precipitation intomethanol. The molecular weight measured by GPC is 2200 g/mol and PDI is1.16. Yield: 15 grams of polymer was obtained after purification.

STEPS 2-4: Synthesis of MMA₂₂-b-tBA₇₆₂/tBA₅₉ Arms, Crosslinking andDeprotection to Produce (MMA₂₂-b-AA₇₆₂/AA₅₉) Star Copolymer in “One Pot”(#12-022-117)

The synthesis includes 3 steps: the synthesis of arms, the cross-linkingof arms and the deprotection of star polymers. For the synthesis ofarms, the molar ratio of reagents is: tBA/MMA₂₂ (from Example 4, Step1)/EBiB/CuBr₂/Me₆TREN/V-70=160/0.2/0.8/0.01/0.05/0.025. Anisole (33%,v/v) was used as solvent. The synthesis of arms was conducted asfollows. In a 22 mL vial 19.05 mg CuBr₂ was dissolved in 6.6 mL DMF with0.1 mL Me₆TREN to make a stock solution. A 250 mL round bottom flask wascharged with 0.78 g of MMA₂₂, 40 mL of tBA and 20 mL of anisole. 1.32 mLof CuBr₂/Me₆TREN in DMF solution was added to the flask. The polymersolution was stirred for 10 min in order to dissolve the macroinitiator.The flask was sealed with a rubber septum and the solution was purgedwith nitrogen for 40 minutes. In a 22 mL vial 13.2 mg of V-70 wasdissolved in 1 mL of acetone and purged with N₂ and then the solution ofV-70 in acetone was transferred into 1 mL syringe under N₂. The flaskwas heated up to 65° C. 0.1 mL of V-70 in acetone was injected every 20minutes. Sample was taken for analysis and as the conversion of monomerreached 43%, 0.2 mL of EBiB was injected. After that, 0.1 mL of V-70 inacetone was injected every 30 minutes. As the monomer conversion reached80%, the flask was open to air. The cross-linking of arms was continuedin the same flask with the molar ratio of reagents as:[MMA₂₂-b-tBA₇₆₂/tBA₅₉]/DVB/CuBr₂/TPMA/Sn(EH₂)=1/25/0.02/0.2/0.2 inanisole. 2.0 mL of CuBr₂/TPMA in DMF solution, 4.28 mL DVB and 28 mLanisole were added to the flask. The polymer solution was purged with N₂for 1 h. Then the flask was heated up to 95° C. 0.08 mL Sn(EH)₂ wasinjected, the reaction started. Sample was taken for analysis and 16hours later as the conversion of DVB reached 80%, the heating wasstopped and the flask was opened to air. Molecular weight of(MMA₂₂-b-tBA₇₆₂/tBA₅₉) star molecule was determined by GPC. Mn=129660g/mol, PDI=2.36. The deprotection was then conducted by adding 15 mL offormic acid and 0.05 mL sulfuric acid to the flask. The reaction mixturewas heated up to 75° C. After 6 hours, the reaction was finished. Theliquid was decanted and the solid polymer was washed with acetonitrileand acetone in the flask for 3 times. The solid polymer was recoveredfrom the flask and dried in vacuum oven at 40° C. for 1 day. Yield: themass of (MMA₂₂-b-AA₇₆₂/AA₅₉) star was 16 grams.

Example 5 Synthesis of (MMA₁₅-b-AA₆₁₇/St₁₆-b-AA₆₁₇/AA₈₆) Star (MolarRatio of Arms: 0.7/0.3/4) (Referenced Herein as(MMA₁₅-b-AA₆₁₇/St₁₆-b-AA₆₁₇/AA₈₆)(7/3) Star)

The simple “one-pot” procedure was used for the preparation of apoly(acrylic acid) based miktoarm star macromolecule similar to thatdescribed in Scheme 2. The miktoarm star macromolecule withMMA₁₅-b-AA₆₁₇, St₁₆-b-AA₆₁₇ and AA₈₆ arms (molar ratio of arms:0.7/0.3/4) was prepared as follows.

STEP 1: Synthesis of a Polystyrene Macroinitiator (St₁₆) Having 16 DP(#12-023-171-2)

St₁₆ macroinitiator was synthesized by using ATRP. The molar ratio ofreagents is: St/EBiB/CuBr₂/Me₆TREN/AIBN=20/1/0.002/0.01/0.05. Anisole(20% v/v) was used as solvent. The reaction was conducted as follows. A1 L Ace Glass reactor was charged with 800 mL of styrene, 51.2 mL ofEBiB and 140 mL of anisole. Then 27.5 mL of CuBr₂/Me₆TREN in DMF wasadded to the reactor. The reactor was closed and the solution was purgedwith nitrogen for 1.0 hour. In a 100 mL flask 2.87 g of AIBN wasdissolved in 40 mL of acetone and purged with N₂. The solution of AIBNin acetone was transferred into 60 mL syringe under N₂. The 1 L reactorwas heated up to 70° C. AIBN in acetone was fed at the rate of 8 mL/h.After 1 hour, 12.5 mL of CuBr₂/Me₆TREN in DMF was added to the 1 Lreactor. 4.8 hours later, feeding of AIBN was stopped and the reactorwas opened. The polymer solution was precipitated into methanol (1/10v/v). The solid polymer was recovered and dried in vacuum oven at 40° C.for 1 day. The molecular weight of St₁₆ is 1650 g/mol and PDI=1.17.Yield: 500 grams of polymer was obtained after purification.

STEPS 2-4: Synthesis of MMA₁₅-b-tBA₆₁₇/St₁₆-b-tBA₆₁₇/tBA₈₆ Arms,Crosslinking and Deprotection to Produce(MMA₁₅-b-AA₆₁₇/St₁₆-b-AA₆₁₇/AA₈₆) Star Copolymer in “One Pot”(#12-027-37)

The synthesis includes 3 steps: the synthesis of arms, the cross-linkingof arms and the deprotection of star polymers. For the synthesis ofarms, the molar ratio of reagents is: tBA/MMA₁₅ (from Example 3, Step1)/St₁₆ (from Example 5, Step1)/EBiB/CuBr₂/Me6TREN/V-70=160/0.14/0.06/0.8/0.01/0.05/0.025. Anisole(33%, v/v) was used as solvent. The synthesis of arms was conducted asfollows. A 250 mL round bottom flask was charged with 0.37 g of MMA₁₅,0.16 g of St₁₆, 40 mL of tBA and 12 mL of anisole. 1.32 mL ofCuBr₂/Me₆TREN in DMF solution was added to the flask. The polymersolution was stirred for 10 min in order to dissolve macroinitiators.The flask was sealed with a rubber septum and the solution was purgedwith nitrogen for 40 minutes. In a 22 mL vial 13.2 mg of V-70 wasdissolved in 1 mL of acetone and purged with N₂. The solution of V-70 inacetone was transferred into 1 mL syringe under N₂. The flask was heatedup to 65° C. 0.1 mL of V-70 in acetone was injected every 20 minutes.Sample was taken for analysis and as the conversion of monomer reached60%, 0.2 mL of EBiB was injected. Then 0.1 mL of V-70 in acetone wasinjected every 30 minutes. As the monomer conversion reached 84%, theflask was opened to air. The cross-linking of arms was continued in thesame flask with the molar ratio of reagents as:[MMA₁₅-b-tBA₆₁₇/St₁₆-b-tBA₆₁₇/tBA₈₆]/DVB/CuBr₂/TPMA/Sn(EH₂)=1/25/0.02/0.2/0.2in anisole. In a 22 mL vial 3.74 mg CuBr₂ was dissolved in 2.0 mL DMFwith 30.0 mg TPMA. Then the DMF solution of CuBr₂/TPMA, 4.28 mL DVB and28 mL anisole were added to the flask. The polymer solution was purgedwith N₂ for 1 hour. The flask was heated up to 95° C. 0.08 mL Sn(EH)₂was injected, the reaction started. 18 hours later, the conversion ofDVB reached 73%, the heating was stopped and the flask was opened toair. Molecular weight of (MMA₁₅-b-tBA₆₁₇/St₁₆-b-tBA₆₁₇/tBA₈₆) starmolecule was determined by GPC. Mn=95274 g/mol, PDI=2.59. Thedeprotection was conducted by adding 15 mL of formic acid and 0.05 mLsulfuric acid to the flask. The reaction mixture was heated to 75° C.and stirred for 6 hours. Then the liquid was decanted and the solidpolymer was washed with acetonitrile and acetone for 3 times in theflask. The polymer was recovered and dried in vacuum oven at 40° C. for1 day. Yield: the mass of (MMA₁₅-b-AA₆₁7/St₁₆-b-AA₆₁₇/AA₈₆) star was 17grams.

Example 6 Synthesis of (MMA₁₅-b-AA₆₇₆/St₁₆-b-AA₆₇₆/AA₅₈) Star (MolarRatio of Arms: 0.9/0.1/4) (Referenced Herein as(MMA₁₅-b-AA₆₇₆/St₁₆-b-AA₆₇₆/AA₅₈) (9/1) Star)

The simple “one-pot” procedure was used for the preparation of apoly(acrylic acid) based miktoarm star macromolecule similar to thatdescribed in Scheme 2. The miktoarm star macromolecule withMMA₁₅-b-AA₆₇₆, St₁₆-b-AA₆₇₆ and AA₅₈ arms (molar ratio of arms:0.9/0.1/4) was prepared as follows.

STEP 1: Synthesis of a Polystyrene Macroinitiator (St₁₆) Having 16 DPand Poly(Methyl Methacrylate) Macroinitiator (MMA₁₅) Having 15 DP

St₁₆ and MMA₂₂ macroinitiators were synthesized as described in Example3, Step 1 and Example 5, Step 1 respectively.

STEPS 2-4: Synthesis of MMA₁₅-b-tBA₆₇₆/St₁₆-b-tBA₆₇₆/tBA₅₈ Arms,Crosslinking and Deprotection to Produce(MMA₁₅-b-AA₆₇₆/St₁₆-b-AA₆₇₆/AA₅₈) Star Copolymer in “One Pot”(#12-022-112)

The synthesis includes 3 steps: the synthesis of arms, the cross-linkingof arms and the deprotection of star polymers. For the synthesis ofarms, the molar ratio of reagents is: tBA/MMA₁₅ (from Example 3, Step1)/St₁₆ (from Example 5, Step1)/EBiB/CuBr₂/Me6TREN/V-70=160/0.18/0.02/0.8/0.01/0.05/0.025. Anisole(33%, v/v) was used as solvent. The synthesis of arms was conducted asfollows. In a 22 mL vial 19.05 mg CuBr₂ was dissolved in 6.6 mL DMF with0.1 mL Me₆TREN to make a stock solution. A 250 mL round bottom flask wascharged with 0.477 g of MMA₁₅, 0.053 g of St₁₆, 40 mL of tBA and 20 mLof anisole. 1.32 mL of CuBr₂/Me₆TREN in DMF solution was added to theflask. The polymer solution was stirred for 10 min in order to dissolvemacroinitiators. The flask was sealed with a rubber septum and thesolution was purged with nitrogen for 40 minutes. In a 22 mL vial 13.2mg of V-70 was dissolved in 1 mL of acetone and purged with N₂. Thesolution of V-70 in acetone was transferred into 1 mL syringe under N₂.The flask was heated up to 65° C. 0.1 mL of V-70 in acetone was injectedevery 20 minutes. Sample was taken for analysis and as the conversion ofmonomer reached 51%, 0.2 mL of EBiB was injected. Then 0.1 mL of V-70 inacetone was injected every 30 minutes. As the monomer conversion reached87%, the flask was open to air. The cross-linking of arms was continuedin the same flask with the molar ratio of reagents as:[MMA₁₅-b-tBA₆₇₆/St₁₆-b-tBA₆₇₆/tBA₅₈]/DVB/CuBr₂/TPMA/Sn(EH₂)=1:25/0.02/0.2/0.2in anisole. In a 22 mL vial 3.74 mg CuBr₂ was dissolved in 2.0 mL DMFwith 30.0 mg TPMA. CuBr₂/TPMA in DMF, 4.28 mL DVB and 28 mL anisole wereadded to the flask. The polymer solution was purged with N₂ for 1 hourand then heated up to 95° C. 0.08 mL Sn(EH)₂ was injected, the reactionstarted. After 17 hours, the conversion of DVB reached 64%, the heatingwas stopped and the flask was opened to air. Molecular weight of(PMMA₁₅-b-PtBA/PSt₁₆-b-PtBA/PtBA) star molecule was determined by GPC.Mn=87575 g/mol, PDI=2.36. The deprotection was conducted by adding 15 mLof formic acid and 0.05 mL sulfuric acid to the flask. The reactionmixture was heated up to 75° C. After 6 hours, the reaction finished.The liquid was decanted and the solid polymer was washed withacetonitrile and acetone for 3 times in the flask. The solid polymer wasrecovered and was dried in vacuum oven at 40° C. for 1 day. Yield: themass of (MMA₁₅-b-AA₆₇₆/St₁₆-b-AA₆₇₆/AA₅₈) star was 16 grams.

Properties of Star Copolymers (Examples 7-12) Example 7 Shear ThinningProperties of Star Macromolecules as Thickening Agents

The thickening properties of the aqueous solutions of starmacromolecules synthesized in Examples 1-6 as well as Carbopol wereinvestigated. Overall, gels were prepared with different concentrationsin order to match the same initial viscosities for all the measuredsamples. Gels were formed following the procedure: 400 mL of deionized(DI) water was transferred to 600 mL beaker and beaker was assembledbelow overhead stirrer IKA with mount stirring shaft with 3-blade marineimpeller. Water was stirred at 600 rpm to generate vortex and a solidpolymer (e.g., 1.2 g) was slowly sprinkled. Water solution was heated to30° C. and next solid NaOH (e.g. 0.32 g) was added. Stirring rate wasincreased to 800 rpm and next to 1600 rpm. Water solution was stirredfor 15-20 min until temperature reached 80-90° C. The beaker with a gelwas then assembled below Silverson homogenizer with mount Square Holeworkhead and Axial Flow workhead. The stirring speed was graduallyincreased to 4800±200 rpm and mixed for 35 min until thick homogeneousgel was obtained. A pH of the resulting gel was analyzed with pH meterand adjusted to pH=7.2±0.3.

The rheological properties of the multi-arm stars and Carbopol were theninvestigated and compared. The viscosity of aqueous solutions of thestar macromolecules vs. shear rate was measured using a BrookfieldLVDV-E, Spindle #25 at T=25° C., and the results are presented in FIG. 4and Table 2. It is clear that even very low concentrations of the starmacromolecules in water (0.3-0.6 wt. %) results in the very highapparent viscosity of the solution (in the range of 230,000 to 430,000centipoise (cP)) and all the samples have very strong shear thinningproperties.

TABLE 2 Viscosity [cP] Shear Product of Example Rate Carbopol 1 2 3 4 56 [s−1] 0.3 wt. % 0.4 wt. % 0.6 wt. % 0.6 wt. % 0.3 wt. % 0.4 wt. % 0.4wt. % 0.066 326000 430000 435000 230000 133000 258000 418000 0.11 241900303400 309000 162200 96000 170900 271700 0.22 159400 186200 187700 9840059500 103700 187700 0.44 100200 108700 105800 59000 38200 63400 1049001.1 50980 50780 43580 29950 25680 32830 46940 2.2 30580 22560 2136018000 16370 17180 25100 4.4 18550 11660 11230 11110 10030 8950 13700 6.613900 7980 7550 8380 7970 6190 8990 11 NA 4973 4886 5971 5299 3878 599022 NA 2717 2688 3787 3235 2083 3058

Example 8 Salt-Tolerance Test—Salt Tolerance of Star Macromolecules asThickening Agents

Six gels were formed following the procedure described in the Example 7.Gels were formed using star macromolecules from Examples 1-5 andCarbopol. Overall, gels were prepared with different concentrations inorder to match the initial viscosities for the measured samples (e.g.Advantomer has similar initial viscosity as star from Example 2, andCarbopol has similar initial viscosity as stars from Examples 3-5). Thefollowing procedure was applied to investigate the viscosity of theaqueous gels in the presence of salt (sodium chloride, NaCl). Asaturated NaCl water solution was prepared by dissolving NaCl indeionized water at 25° C. The concentration was 357 mg/mL (0.264 gNaCl/g solution). A series of salt containing gels were prepared byadding a certain amount of saturated NaCl solution to 20 g of gel in thevial (analytical balance with 0.1 mg accuracy was used during addition).The NaCl solution and the gel were mixed by shaking the vial vigorouslyfor 5 minutes. The viscosity of the gels in different amounts of saltare presented in FIG. 5 (and Table 3). The viscosity of aqueoussolutions was measured using a Brookfield LVDV-E, Spindle #25 (or #34)at 1 rpm and at T=25° C. Both Carbopol and Advantomer (Example 1) weremuch less tolerant to salt than the star macromolecules synthesized inExamples 2-5 which comprise MAA units in the hydrophobic segment(Example 2) or MMA units as hydrophobic segment (Examples 3-5).

TABLE 3 Viscosity at 1 rpm [cP] Product of Example NaCl Carbopol 1 2 3 45 6 [wt. %] 0.3 wt. % 0.3 wt. % 0.6 wt. % 0.6 wt. % 0.3 wt. % 0.4 wt. %0.3 wt. % 0 127700 185800 187700 98400 59500 103700 420 0.05 71500 52300177600 149800 97000 82100 20600 0.1 19200 20600 167500 153100 7630087800 25000 0.2 5300 4300 128200 120000 38900 49000 28800 0.4 420 48073400 72000 18200 20600 24000 0.5 320 360 50900 15400 1 240 280 720015400 13400 12500 10600

Next, seven gels were formed following the procedure described in theExample 7. Gels were formed using star macromolecules from Examples 1-6and Carbopol. Overall, gels were prepared with exactly the sameconcentration of 0.4 wt. %. Next, following the procedure in Example 8,a saturated NaCl water solution was added to all gels. In each case thesame amount was added and the resulting concentration of NaCl in eachsample was 0.4 wt. %. The viscosity of aqueous solutions was measured asdescribed in the Example 8. The results are presented in Table 4. BothCarbopol and Advantomer (from Example 1) were much less tolerant to saltthan the star macromolecules synthesized in Examples 2-6 which compriseMAA units in the hydrophobic segment (Example 2) or MMA units ashydrophobic segment (Examples 3-6).

TABLE 4 Product of Viscosity Example Name [cP] — Carbopol 12000 1Advantomer 15400 2 ((St₁₉-co-MAA₄)-b-AA₃₂₅/AA₉₈) star 13400 3(MMA₁₅-b-AA₃₆₇/AA₈₂) star 51800 4 (MMA₂₂-b-AA₇₆₂/AA₅₉) star 45100 5(MMA₁₅-b-AA₆₁₇/St₁₆-b-AA₆₁₇/AA₈₆) (7/3) star 20600 6(MMA₁₅-b-AA₆₇₆/St₁₆-b-AA₆₇₆/AA₅₈) (9/1) star 53800

Example 9 Temperature Stability Test—Temperature Stability of StarMacromolecules as Thickening Agents

Six gels were formed following the procedure described in the Example 7.Gels were formed using star macromolecules from Example 1-5 andCarbopol. Overall, gels were prepared with different concentrations inorder to match the initial viscosities for the measured samples (e.g.Carbopol and Advantomer has similar initial viscosity as stars fromExample 3 and 5, and star from Example 2 has similar initial viscosityas star from Examples 4). The viscosity of aqueous solutions wasmeasured using a Brookfield LVDV-E, Spindle #25 (or #34) at 1 rpm and atdifferent temperatures (the measurements were taken after thetemperature of water bath and polymer solution was equilibrated for atleast 15 min). The results are presented in FIG. 6 and Table 5.

TABLE 5 Viscosity at 1 rpm [cP] Product of Example Carbopol 1 2 3 4 5Temp. ° C. 0.3 wt. % 0.3 wt. % 0.6 wt. % 0.6 wt. % 0.3 wt. % 0.4 wt. %25 113800 117600 217900 98400 255400 103700 35 95500 88600 190600 83000231300 103200 40 89800 87800 161300 76800 210200 98900 45 80600 87800153100 69600 192100 98400 50 76300 86400 151200 51400 189100 97400 5573000 81600 143000 48500 183400 95200 60 70600 79700 133900 40800 17910091500 80 63800 71500 117100 4800 172900 60000

Next, seven gels were formed following the procedure described in theExample 7. Gels were formed using star macromolecules from Examples 1-6and Carbopol. Overall, gels were prepared with exactly the sameconcentration of 0.4 wt. %. Next, following the procedure in Example 8,a saturated NaCl water solution was added to all gels. In each case thesame amount was added and the resulting concentration of NaCl in eachsample was 0.4 wt. %. The viscosity of aqueous solutions was measuredusing a Brookfield LVDV-E, Spindle #25 (or #34) at 1 rpm and at threedifferent temperatures: 25, 40 and 55° C. (the measurements were takenafter the temperature of water bath and polymer solution wasequilibrated for at least 15 min). The results are presented in Table 6,along with the calculated Temperature Stability Values according to thefollowing equation:[1−(Dynamic Viscosity(at 55° C.)−Dynamic Viscosity (at 25° C.))/DynamicViscosity (at 25° C.)]×100%.

TABLE 6 Product of Viscosity at Viscosity at Viscosity at TemperatureExample 25° C. [cP] 40° C. [cP] 55° C. [cP] Stability Value — 1200010100 8200 68.3% 1 15400 10100 8600 55.8% 2 13400 12000 10600 79.1% 351800 44600 39800 76.8% 4 45100 32200 29800 66.1% 5 20600 20200 1630079.1% 6 53800 51600 42700 79.4%

Example 10 Star Macromolecules as Thickening and Emulsifying Agents

Due to its very well-defined structure, the star macromolecules fromExample 1-6 may act not only as thickening agents but also as efficientemulsifying agents. FIG. 7 presents an image demonstrating theemulsifying properties of the star copolymer from Example 4. Thephotograph presents water with 30 vol. % of sunflower oil (left vial)and water with 30 vol. % of sunflower oil and 0.3 wt. % of thickeningagent (right vial). After vigorous mixing (as described in the EmulsionTest Procedure), phase separation occurred in the left vial while it didnot occur in the right vial. At the same time the thickening propertiesdid not decrease. The photograph was taken 2 days after the emulsion wasprepared.

Example 11 Salt Tolerance of Star Macromolecules as Thickening Agents inRiver Water

Four gels were formed following the procedure described in Example 7,but instead of deionized (DI) water, river water was used (water wastaken from the Allegheny River near Pittsburgh). Gels were formed usingstar macromolecules from Examples 1, 3, 5, and Carbopol. Overall, gelswere prepared with different concentrations in order to match theinitial viscosities for the measured samples. Next, gels were mixed withdifferent amounts of NaCl as described in the Example 8. FIG. 8 andTable 7 present the viscosity of gels with river water in the presentsof different amounts of NaCl. The viscosity of aqueous solutions wasmeasured using a Brookfield LVDV-E, Spindle #25 (or #34) at 1 rpm and atT=25° C.

TABLE 7 Viscosity at 1 rpm [cP] Product of Example NaCl Carbopol 1 3 5[wt. %] 0.3 wt. % 0.4 wt. % 0.6 wt. % 0.4 wt. % 0 198700 158900 4800244800 0.025 84500 242900 0.05 121000 291800 0.1 135400 253900 0.2 530027800 247200 216400 0.4 123400 0.5 117600 1 44600 39400 2 18700 125002.5 11500 7500

Example 12 pH Efficiency Range Test—Star Macromolecules as ThickeningAgents at Different pH

An aqueous gel composition at 0.6 wt. % was prepared (similarly to thatdescribed in the Sample Preparation Procedure) for the starmacromolecule of Example 6, at a starting pH of around 5. A separateaqueous gel composition at 0.2 wt. % aqueous gel composition of Carbopolwas prepared at a starting pH of around 3. Then, the viscosity of thesamples was measured in accordance to the Dynamic Viscosity TestProcedure and the dynamic viscosity at 1 rpm was recorded. Thisprocedure was repeated for differing pH values, adjusted by addition ofsodium hydroxide (or hydrochloric acid). The results are presented inFIG. 9 and Table 8. The prepared star macromolecules efficientlythickened water at broader pH ranges than Carbopol (between pH 3 and13).

TABLE 8 Viscosity [cP] Viscosity [cP] pH Carbopol (0.2 wt. %) pH Example6 (0.6 wt. %) 3 450 2.85 5300 4.7 66200 4.59 5900 5.9 108500 4.98 1152006.9 86900 5.83 189600 7.7 75800 6.2 185000 8.8 62300 6.9 187700 9.853800 7.5 119000 11.1 44100 8.69 77800 12 19920 12.53 66700 13 3480 — —

Test Procedures:

Sample Preparation Procedure

Aqueous gel compositions were prepared at various concentrations of apolymer (e.g., 0.3 wt. %, 0.4 wt %, and 0.6 wt. %) by heating andstirring. Gels were formed following the procedure. 400 ml of deionized(DI) water was transferred to 600 ml beaker and beaker was assembledbelow overhead stirrer IKA with mount stirring shaft with 3-blade marineimpeller. Water was stirred at 600 rpm to generate vortex and a polymer(e.g. 1.2 g for a given wt. % gel) was slowly added. Water solution washeated to 30° C. and next solid NaOH (e.g. 0.32 g) was added. Watersolution was stirred for 20 min until temperature reached 90° C. Thebeaker with a gel was then assembled below Silverson homogenizer withmount Square Hole workhead and Axial Flow workhead. The stirring speedwas gradually increased to 4800±200 rpm and mixed for 35 min until thickhomogeneous gel was obtained. A pH of the resulting gel was analyzedwith pH meter and adjusted to about pH=7.2±0.3.

Dynamic Viscosity Test Procedure

To the removable chamber of the Brookfield LVDV-E Digital Viscometer wastransferred 16.1 ml of the gel prepared according to the SamplePreparation Procedure. Then the spindle #25 was attached to the pivotCup on Brookfield viscometer. The viscosity was measured at 25° C. andat standard pressure over a wide range of rates (e.g, 0.3-100 rpm) andthe shear rate and viscosity was recorded. The viscosity measurementswere taken in the following sequence, stopping the instrument after eachmeasurement for 5 minutes, 0.3, 0.5, 1, 2, 5, 10, 20, 30, 50, and 100rpm. Dynamic viscosity was determined as the viscosity in centipoise(cP) at 1 rpm.

Shear-Thinning Value

A shear-thinning value was determined by dividing the viscosity value at0.3 rpm by the viscosity value at 20 rpm as measured during the DynamicViscosity Test Procedure.

Salt Tolerance Test

The following procedure was applied to measure the viscosity of theaqueous gels in the presence of salt (sodium chloride, NaCl). Asaturated NaCl water solution was prepared by dissolving NaCl indeionized water at 25° C. The concentration was 357 mg/ml (0.264 gNaCl/g solution). A salt containing gel (0.4 wt % of NaCl) was preparedby adding 301.9 mg of saturated NaCl solution to a vial with 20 g of a0.4 wt % gel which was prepared as described in the Sample PreparationProcedure (analytical balance with 0.1 mg accuracy was used during theaddition). The NaCl solution and the gel were mixed by shaking the vialvigorously for 5 minutes. A portion of the gel (16.1 ml) was transferredto the removable chamber of the Brookfield LVDV-E Digital Viscometer.Then spindle #25 was attached to the pivot Cup on the Brookfieldviscometer. The Salt Tolerant Test value for the tested salt-tolerantmacromolecule was measured and recorded as the viscosity (in centipoise,cP) at a given wt. % gel in a given wt. % NaCl concentration (forexample a viscosity of 12,000 cP at 0.4 wt % gel in a 0.4 wt % NaClconcentration).

Temperature Stability Value Test Procedure

A 0.4 wt % gel with 0.4 wt % of NaCl was prepared as described in SaltTolerance Test. Next, 16.1 ml of gel was transferred to the removablechamber of the Brookfield LVDV-E Digital Viscometer. Then the spindle#25 was attached to the pivot Cup on Brookfield viscometer. Theviscosity was measured at 1 rpm and at standard pressure over a widerange of temperatures. Viscosity measurements were taken at thefollowing temperatures, 25, 40, and 55° C., stopping the instrumentafter each measurement and equilibrating temperature for at least 15min. The temperature Stability Value, in percent, is determined as theviscosity in centipoise (cP) at 1 rpm at 25 and 55° C. following theequation:[1−(Dynamic Viscosity (at 55° C.)−Dynamic Viscosity (at 25° C.))/DynamicViscosity (at 25° C.)]×100%.

Emulsion Test Procedure and Emulsion Value

280 ml of deionized (DI) water was transferred to 600 ml beaker andbeaker was assembled below overhead stirrer IKA with mount stirringshaft with 3-blade marine impeller. Water was stirred at 600 rpm togenerate vortex and 1.2 g of a polymer was slowly added. Water solutionwas heated to 30° C. and next 0.32 g of solid NaOH was added (pHadjusted to pH=7). Stirring rate was increased to 800 rpm and next to1600 rpm. 120 ml of sunflower oil was added while the stirring wascontinued for 20 min at 80° C. or until homogeneous solution wasobtained. The mixture was allowed to cool to room temperature. Once thesystem cooled to room temperature a timer was started. The EmulsionValue is the time, in minutes, it takes for the system to form twovisible layers (phase separation).

Hydrophilic-Lipophilic (HLB) Arm/Segment CalculationHLB=20*Mh/Mwhere Mh is the molecular mass of the hydrophilic portion of thepolymeric arm or segment, and M is the molecular mass of the wholepolymeric arm or segment.

Hydrophilic-Lipophilic Macromolecule Calculation

${HLM} = {{\sum\limits_{n = 1}^{n = m}{M\; W_{n} \times {{HLB}_{n}/20}\mspace{14mu}{divided}\mspace{14mu}{by}\mspace{14mu} 0.3M\; W_{core}}} + {\sum\limits_{n = 1}^{n = m}{M\; W_{n}}}}$where

-   -   MW_(n) is the molecular weight for the respective arm,    -   HLB_(n) is the HLB, as calculated from the HLB arm calculation,        for the respective arm, and    -   MW_(core) is the molecular weight for the core, and    -   M is the total number of arms.

pH Efficiency Range Test Procedure

An aqueous gel composition at 0.4 wt. % was prepared (similarly to thatdescribed in the Sample Preparation Procedure) for a star macromoleculeof the present invention, at a starting pH of around 5 and a separateaqueous gel composition at 0.2 wt. % aqueous gel composition of CarbopolETD 2020, at a starting pH of around 3, was prepared by mixing andheating, as necessary (e.g., vigorous mixing at a temperature of about60° C.). Then, the viscosity of the sample was measured in accordancewith the Dynamic Viscosity Test Procedure, above, and the dynamicviscosity at 1 rpm was recorded. This procedure was repeated fordiffering pH values, adjusted by addition of sodium hydroxide. ThepH-induced break value, in percent, is determined by the followingequation:Dynamic Viscosity (at 1 rpm) at pH 7.5−Dynamic Viscosity (at 1 rpm) atpH 5/Dynamic Viscosity (at 1 rpm) at pH 7.5×100%.

Any and all publications and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication or patent application was specificallyand individually indicated to be incorporated by reference.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. It is intendedthat the following claims define the scope of the invention and thatmethods and structures within the scope of these claims and theirequivalents be covered thereby.

What is claimed is:
 1. A salt-tolerant star macromolecule that whendissolved in water at a concentration of at least 0.3 wt. % forms ahomogeneous gel and has a dynamic viscosity of at least 10,000 cP in a0.4 wt. % NaCl aqueous solution, according to the Salt Tolerance Test;wherein the salt-tolerant star macromolecule comprises a plurality ofpolymeric arms comprising at least two types of arms, wherein: i) afirst polymeric arm that extends beyond a second polymeric arm; and ii)the first polymeric arm has a salt-tolerant-enhancing segment on itsdistal end.
 2. The salt-tolerant star macromolecule of claim 1, whereinthe salt-tolerant star macromolecule has a dynamic viscosity in aNaCl-containing aqueous solution that is greater than the dynamicviscosity at 0.0 wt. % NaCl aqueous solution, according to the SaltTolerance Test.
 3. The salt-tolerant star macromolecule of claim 1,wherein the salt-tolerant star macromolecule has an increase in dynamicviscosity with an increase in NaCl concentration, according to the SaltTolerance Test.
 4. The salt-tolerant star macromolecule of claim 1,wherein the dynamic viscosity of the salt-tolerant star macromolecule ina 0.2 wt. % NaCl aqueous solution is at least 40% of the dynamicviscosity at 0.0 wt. % NaCl aqueous solution, according to the SaltTolerance Test.
 5. The salt-tolerant star macromolecule of claim 1,wherein the salt-tolerant star macromolecule comprises: i) a core; ii)the first polymeric arm is a salt-tolerant-enhancing copolymeric arm,comprising: a) a hydrophilic polymeric segment proximal to the core; andb) a salt-tolerant-enhancing polymeric segment distal to the core; andiii) the second polymeric arm is a hydrophilic polymeric arm.
 6. Thesalt-tolerant star macromolecule of claim 5, wherein thesalt-tolerant-enhancing polymeric segment comprises: i) repeat units ofmonomeric residues of one or more polymerized salt-tolerant-enhancingmonomers; and ii) optionally, repeat units of monomeric residues of oneor more polymerized hydrophobic or hydrophilic monomers.
 7. Thesalt-tolerant star macromolecule of claim 1, wherein the salt-tolerantstar macromolecule is represented by Formula Z:

wherein: Core represents a crosslinked polymeric segment; P1 representsa hydrophilic polymeric segment comprised of repeat units of monomericresidues of one or more polymerized hydrophilic monomers; P2independently represents a salt-tolerant-enhancing polymeric segmentcomprising repeat units of: a) monomeric residues of one or morepolymerized salt-tolerant-enhancing monomers; and b) optionally,monomeric residues of one or more polymerized hydrophobic or hydrophilicmonomers; P3 independently represents a hydrophilic polymeric segmentcomprised of repeat units of monomeric residues of one or morepolymerized hydrophilic monomers; P4 represents a hydrophobic polymericsegment comprised of repeat units of monomeric residues of one or morepolymerized hydrophobic monomers; P5 represents a hydrophilic polymericsegment comprised of repeat units of monomeric residues of one or morepolymerized hydrophilic monomers; q1 represents the number of repeatunits in P1 and has a value between 10 and 2000; q2 independentlyrepresents the number of repeat units in P2 and has a value between 10and 500; q3 independently represents the number of repeat units in P3and has a value between 10 and 2000; q4 represents the number of repeatunits in P4 and has a value between 10 and 500; q5 represents the numberof repeat units in P5 and has a value between 10 and 2000; r representsthe number of polymeric arms covalently attached to the Core and has avalue in the range of from 0 to 1000; s independently represents thenumber of salt-tolerant-enhancing copolymeric arms covalently attachedto the Core and has a value in the range of from 1 to 1000; t representsthe number of copolymeric arms covalently attached to the Core and has avalue in the range of from 0 to 1000; and n represents the number ofsalt-tolerant-enhancing arm types covalently attached to the Core andhas a value of at least 1; wherein: i) the molar ratio of: a) r to s isin the range of between 40:1 and 1:40; b) the molar ratio of r to t isin the range of between 40:1 and 1:40; c) the molar ratio of t to s isin the range of between 40:1 and 1:40; d) the molar ratio of r to (s+t)is in the range of between 40:1 and 1:40; or e) combinations thereof;and ii) r and t cannot both equal zero unless n represents a value of atleast
 2. 8. The salt-tolerant star macromolecule of claim 1, wherein thesalt-tolerant star macromolecule has a molecular weight (Mn) in therange of from 5,000 g/mol to 10,000,000 g/mol.
 9. The salt-tolerant starmacromolecule of claim 1, wherein the arms of the salt-tolerant starmacromolecule independently have a molecular weight (Mn) in the range offrom 1,000 g/mol to 250,000 g/mol.
 10. The salt-tolerant starmacromolecule of claim 7, wherein the monomeric residues of one or morepolymerized hydrophobic or hydrophilic monomers are present in thesalt-tolerant-enhancing polymeric segment P2.
 11. The salt-tolerant starmacromolecule of claim 1, wherein the salt-tolerant star macromoleculecomprises a plurality of polymeric arms comprising at least three typesof arms, wherein: i) the first polymeric arm extends beyond the secondpolymeric arm and said first polymeric arm has thesalt-tolerant-enhancing segment on its distal end; and ii) a thirdpolymeric arm that extends beyond said second polymeric arm and saidthird polymeric arm has a hydrophobic segment on its distal end.
 12. Thesalt-tolerant star macromolecule of claim 1, wherein the dynamicviscosity of the salt-tolerant star macromolecule at 80° C. is at least50% relative to viscosity of the gel at 25° C., according to theTemperature Stability Test.
 13. The salt-tolerant star macromolecule ofclaim 1, wherein the dynamic viscosity of the salt-tolerant starmacromolecule at 60° C. is at least 60% relative to viscosity of the gelat 25° C., according to the Temperature Stability Test.
 14. Asalt-tolerant thickening agent, comprising the salt-tolerant starmacromolecule of claim
 1. 15. A method of making a salt-tolerantcomposition, comprising: adding the salt-tolerant star macromolecule ofclaim 1, that when dissolved in water at a concentration of at least 0.3wt. % forms a homogeneous gel and has a dynamic viscosity of at least10,000 cP in a 0.4 wt. % NaCl aqueous solution, according to the SaltTolerance Test.
 16. A method of making an aqueous compositionsalt-tolerant, comprising: adding at least 0.3 wt. % of thesalt-tolerant star macromolecule of claim 1 to the aqueous composition;wherein the salt-tolerant star macromolecule when dissolved in water ata concentration of at least 0.3 wt. % forms a homogeneous gel and has adynamic viscosity of at least 10,000 cP in a 0.4 wt. % NaCl aqueoussolution, according to the Salt Tolerance Test.
 17. The salt-tolerantstar macromolecule of claim 7, wherein the monomeric residues of one ormore polymerized salt-tolerant-enhancing monomers present within thesalt-tolerant-enhancing polymeric segment P2 comprises: methyl acrylate,methyl methacrylate, methyl ethacrylate, ethyl acrylate, ethylmethacrylate, ethyl ethacrylate, n-butyl acrylate, n-butyl methacrylate,n-butyl ethacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate,2-ethylhexyl ethacrylate, N-octyl acrylamide, 2-methoxyethyl acrylate,2-hydroxyethyl acrylate, N,N-dimethylaminoethyl acrylate,N,N-dimethylaminoethyl methacrylate, acrylic acid, methacrylic acid,N-t-butylacrylamide, N-sec-butylacrylamide, N,N-dimethylacrylamide,N,N-dibutylacrylamide, N,N-dihydroxyethyllacrylamide 2-hydroxyethylacrylate, 2-hydroxyethyl methacrylate, benzyl acrylate,4-butoxycarbonylphenyl acrylate, butyl acrylate, 4-cyanobutyl acrylate,cyclohexyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, heptylacrylate, iso-butyl acrylate, 3-methoxybutyl acrylate, 3-methoxypropylacrylate, methyl acrylate, N-butyl acrylamide, ethyl acrylate,methoxyethyl acrylate, hydroxyethyl acrylate, diethyleneglycolethylacrylate, 2-fluoroethyl acrylate, or 2-fluoroethyl methacrylate.
 18. Thesalt-tolerant star macromolecule of claim 7, wherein the monomericresidues of one or more polymerized salt-tolerant-enhancing monomerspresent within the salt-tolerant-enhancing polymeric segment P2comprises: methyl acrylate or methyl methacrylate.
 19. The salt-tolerantstar macromolecule of claim 10, wherein the monomeric residues of theone or more polymerized hydrophobic or hydrophilic monomers monomers ispresent in the salt-tolerant-enhancing polymeric segment P2 andcomprises: styrene, methyl acrylate, ethyl acrylate, n-butyl acrylate,iso-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, decylacrylate, octyl acrylate, methyl methacrylate, ethyl methacrylate,n-butyl methacrylate, iso-butyl methacrylate, t-butyl methacrylate,2-ethylhexyl methacrylate, decyl methacrylate, methyl ethacrylate, ethylethacrylate, n-butyl ethacrylate, iso-butyl ethacrylate, t-butylethacrylate, 2-ethylhexyl ethacrylate, decyl ethacrylate,2,3-dihydroxypropyl acrylate, 2,3-dihydroxypropyl methacrylate,2-hydroxypropyl acrylate, hydroxypropyl methacrylate, glycidylmethacrylate, glycidyl acrylate, acrylamide, styrene, or styreneoptionally substituted with one or more C1-C12 straight or branchedchain alkyl groups.
 20. The salt-tolerant star macromolecule of claim10, wherein the monomeric residues of the one or more polymerizedhydrophobic monomers present in the salt-tolerant-enhancing polymericsegment P2 comprises styrene.